Add Overwrites files for some classes

+	Starting from this commit, there will be overwrite files added to
	provide further details about certain APIs.

docs/_overwrites/Commands/CommandException.Overwrite.md

@@ -0,0 +1,27 @@
+---
+uid: Discord.Commands.CommandException
+---
+
+### Remarks
+
+This @System.Exception class is typically used when diagnosing
+an error thrown during the execution of a command. You will find the
+thrown exception passed into
+[LogMessage.Exception](xref:Discord.LogMessage.Exception), which is
+sent to your [CommandService.Log](xref:Discord.Commands.CommandService.Log)
+event handler.
+
+You may use this information to handle runtime exceptions after
+execution. Below is an example of how you may use this:
+
+```cs
+public Task LogHandlerAsync(LogMessage logMessage)
+{
+    // Note that this casting method requires C#7 and up.
+    if (logMessage?.Exception is CommandException cmdEx)
+    {
+        Console.WriteLine($"{cmdEx.GetBaseException().GetType()} was thrown while executing {cmdEx.Command.Aliases.First()} in {cmdEx.Context.Channel} by {cmdEx.Context.User}.");
+    }
+    return Task.CompletedTask;
+}
+```

docs/_overwrites/Commands/DontAutoLoadAttribute.Overwrite.md

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+---
+uid: Discord.Commands.DontAutoLoadAttribute
+---
+
+### Remarks
+
+The attribute can be applied to a public class that inherits
+@Discord.Commands.ModuleBase. By applying this attribute,
+@Discord.Commands.CommandService.AddModulesAsync* will not discover and
+add the marked module to the CommandService.
+
+### Example
+
+```cs
+[DontAutoLoad]
+public class MyModule : ModuleBase<SocketCommandContext>
+{
+    // ...
+}
+```

docs/_overwrites/Commands/DontInjectAttribute.Overwrite.md

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+---
+uid: Discord.Commands.DontInjectAttribute
+---
+
+### Remarks
+
+The attribute can be applied to a public settable property inside a
+@Discord.Commands.ModuleBase based class. By applying this property,
+the marked property will not be automatically injected of the
+dependency. See [Dependency Injection](../../guides/commands/commands.md#dependency-injection)
+to learn more.
+
+### Example
+
+```cs
+public class MyModule : ModuleBase<SocketCommandContext>
+{
+    [DontInject]
+    public MyService MyService { get; set; }
+
+    public MyModule()
+    {
+        MyService = new MyService();
+    }
+}
+```

docs/_overwrites/Commands/ShardedCommandContext.Overwrite.md

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+---
+uid: Discord.Commands.ShardedCommandContext
+---
+
+### Example
+An example of how this class is used the command system can be seen
+below:
+
+[!code[Sample module](../../guides/commands/samples/empty-module.cs)]
+[!code[Command handler](../../guides/commands/samples/command_handler.cs)]

docs/_overwrites/Common/Discord.EmbedBuilder.Overwrites.md

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+---
+uid: Discord.EmbedBuilder
+---
+
+### Remarks
+
+This builder class is used to build an @Discord.Embed (rich embed)
+object that will be ready to be sent via @Discord.IMessageChannel.SendMessageAsync* 
+after @Discord.EmbedBuilder.Build* is called.
+
+### Example
+
+```cs
+public async Task SendRichEmbedAsync()
+{
+    var embed = new EmbedBuilder
+                    {
+                        // Embed property can be set within object initializer
+                        Title = "Hello world!"
+                    }
+                    // Or with the method
+                    .WithTitle("I overwrote the title.")
+                    .WithDescription("I am a description.")
+                    .WithUrl("https://example.com")
+                    .Build();
+    await _channel.SendMessageAsync(string.Empty, embed: embed);
+}
+```