New CSS linter which is much more powerfull than the previous one.
Configuration is default but I had to remove a few rules that were
throwing too many or weird errors.

More importantly, the linter will exit with code 1 on errors so now our
build will fail if the CSS linter fails which should eliminate linter
errors being introduced without notice.

* add 'npm' and 'npm-update' make targets and lockfile

- `make npm` installs and updates node_modules, triggered automatically
   on `make css` and `make js` as it completes reasonably fast and
   ensures consistent modules.
- `make npm-update` updates all dependencies to their latest version,
   regenerates `node_modules` from scratch and updates
   `package-lock.json`. It uses npm modules `updates` written by yours
   truly to find the latest version of each dependency.

* add suggested make dependencies

* remove package-lock.json during npm-update

* regenerate package-lock.json

* remove and disable package-lock

Using exact versions in package.json has the same effect as lockfiles
without all the troubles the lockfiles bring (different versions of
package manager generating different lockfiles primarily).

Ensured we only use exact versions in package.json and stopped
generation of new lockfiles via .npmrc which is support by both the npm
and yarn package managers.

Fixes: https://github.com/go-gitea/gitea/issues/6967

* enable save-exact

* add make targets for js,css, add javascript linter

- add `make js`, deprecating `make javascripts`
- add `make css`, deprecating `make generate-stylesheets` and
  `make stylesheets-check`
- changed the unclean css check to only run on CI
- add JS linting via eslint with basic configuration and fixed
  discovered issues
- changed autoprefixer to use official `postcss-cli` avoiding the need
  to loop in the makefile
- moved browserslist to package.json so other future tools can use it
  too.
- update documentation for new make targets and added JS section

* fix indentation

* move functions used in html to 'exported' list

* Run lessc binary without having to install anything to node_modules

* use relative paths to node bin scripts, removing npx

* Revert "use relative paths to node bin scripts, removing npx"

This reverts commit 119b725525.

* fix lessc and postcss plugins

* check for node_modules and use actual bin names

* Add autoprefixer to css build

* also use autoprefixer on theme files

* Add Attachment API
* repos/:owner/:repo/releases (add attachments)
* repos/:owner/:repo/releases/:id (add attachments)
* repos/:owner/:repo/releases/:id/attachments
* repos/:owner/:repo/releases/:id/attachments/:attachment_id

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Add unit tests for new attachment functions
Fix comments

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* fix lint

* Update vendor.json

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* remove version of sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Fix unit tests
Add missing license header

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add CreateReleaseAttachment
Add EditReleaseAttachment
Add DeleteReleaseAttachment

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add filename query parameter for choosing another name for an attachment

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Fix order of imports

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Restricting updatable attachment columns

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* gofmt

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update go-sdk
Replace Attachments with Assets

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Update go-sdk

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Updating go-sdk and regenerating swagger

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add missing file of go-sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Change origin of code.gitea.io/sdk to code.gitea.io/sdk
Update code.gitea.io/sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update swagger

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update updateAttachment

* Use standard lessc and minify CSS using Node.js

This changes the previous nonstandard `lessc` to the official one and
enables CSS minification via the clean-css module.

To build CSS, Node.js is required along with a `npm install` to get the
tools installed locally in node_modules so there is no dependency on
binaries in PATH. Benefits include:

- Allows one to have a standard lessc in PATH.
- Can now use command line switches on lessc.
- Minified CSS brings faster page load times and also has the benefit
  of discouraging contributors from editing CSS directly.

To build CSS, Node.js is required along with a `npm install` to get the
tools installed locally based on the information in `package.json`.

The 'make stylesheet' task was modified to run without condition. This
makes it easier to work on the make task itself without having to delete
files.

Also fixes: https://github.com/go-gitea/gitea/issues/2198

* install node, npm and modules on drone

* .PHONY

* use 'minify' to minify CSS