Add rainbowme command (#1109)

<!-- Please read
https://github.com/SableClient/Sable/blob/dev/CONTRIBUTING.md before
submitting your pull request -->

### Description

<!-- Please include a summary of the change. Please also include
relevant motivation and context. List any dependencies that are required
for this change. -->

Adds /rainbowme. Self explanatory

#### Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

### Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings

### AI disclosure:

- [ ] Partially AI assisted (clarify which code was AI assisted and
briefly explain what it does).
- [ ] Fully AI generated (explain what all the generated code does in
moderate detail).
<!-- Write any explanation required here, but do not generate the
explanation using AI!! You must prove you understand what the code in
this PR does. -->

Author: 7w1

.changeset/rainbowme-command.md

@@ -0,0 +1,5 @@
+---
+sable: patch
+---
+
+Add a `/rainbowme` command for sending rainbow-formatted action messages.

src/app/features/room/RoomInput.tsx

@@ -890,7 +890,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
         toMatrixCustomHTML(serializedChildren, {
           stripNickname: true,
           nickNameReplacement: nicknameReplacement,
-          forEmote: commandName === Command.Me,
+          forEmote: commandName === Command.Me || commandName === Command.RainbowMe,
           room,
         })
       );
@@ -971,7 +971,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
               toMatrixCustomHTML(serializedChildren, {
                 stripNickname: true,
                 nickNameReplacement: nicknameReplacement,
-                forEmote: commandName === Command.Me,
+                forEmote: commandName === Command.Me || commandName === Command.RainbowMe,
                 room,
               })
             );

src/app/hooks/useCommands.ts

@@ -265,6 +265,7 @@ export enum Command {
   Pronoun = 'pronoun',
   SPronoun = 'spronoun',
   Rainbow = 'rainbow',
+  RainbowMe = 'rainbowme',
   RawMsg = 'rawmsg',
   Raw = 'raw',
   RawAcc = 'rawacc',
@@ -1162,6 +1163,21 @@ export const useCommands = (mx: MatrixClient, room: Room): CommandRecord => {
           });
         },
       },
+      [Command.RainbowMe]: {
+        name: Command.RainbowMe,
+        description: 'Send a rainbow action message.',
+        exe: async (payload, html) => {
+          if (!payload || payload.trim().length === 0) return;
+          const inputHtml = html || payload;
+          const rainbowHtml = rainbowify(inputHtml);
+          await mx.sendMessage(room.roomId, {
+            msgtype: MsgType.Emote,
+            body: payload,
+            format: 'org.matrix.custom.html',
+            formatted_body: rainbowHtml,
+          });
+        },
+      },
       [Command.RawMsg]: {
         name: Command.RawMsg,
         description: