* fix moltenvk static linking

* build android vulkan 32bit with api-14

* fix artifact name conflicts

* add watchos tvos

* Add POWER8 VSX toolchains

POWER8, though slower than POWER9, is still used in the wild; these
toolchains should still be much faster on POWER8 than POWER8 without VSX
optimizations.

* VSX toolchains: set -cpu arg in QEMU CI tests

* Add POWER9 VSX toolchains

Translating x86_64 SSE to ppc64le VSX intrinsics yields a quite large
speedup on POWER9. See this article for background:

https://www.talospace.com/2019/07/easier-power-vectorizing-for-fun-and.html

* Add power9le docs

* power9le clang toolchain: Document Clang 13+ requirement

---------

Co-authored-by: Jeremy Rand <jeremyrand@danwin1210.de>

1. The correctly link is `how-to-build#build-for-linux` not `#pass-for-linux`, and so on other `#`
2. Add compatibility introduction for Raspberry Pi 4 (build pass)

* Dedicated to coloring black and white photographs.

* Update README.md

* Update how-to-build.md

* Update README.md

* Update README.md

* Update ncnn-android-scrfd link and demo picture

* Update ncnn-android-scrfd link and demo screenshot