docs: add discord links

Author: rxliuli

src/plugins/reddit-ctrl-enter-sender/README.md

@@ -21,3 +21,7 @@ A userscript that enables quick submission of replies, comments, or edits on Red
 2. **Start Typing**: Enter your content in a comment box, reply field, or edit area
 3. **Use the Shortcut**: Press Ctrl+Enter (Windows/Linux) or Cmd+Enter (Mac)
 4. **Auto Submit**: The script automatically finds and clicks the appropriate submit/save button
+
+## Discord
+
+Join the discussion: <https://discord.gg/Cwre8EwkNX>

src/plugins/reddit-search-options-persist/README.md

@@ -25,3 +25,7 @@ Reddit resets all search options every time you enter a new search term. This us
 2. **Perform a Search**: Use the search bar with your preferred filters (sort, time, type)
 3. **Search Again**: Enter a new search term and press Enter
 4. **Filters Preserved**: Your previous filter settings are automatically applied to the new search
+
+## Discord
+
+Join the discussion: <https://discord.gg/Cwre8EwkNX>

src/plugins/youtube-music-background-play/README.md

@@ -30,3 +30,7 @@ The userscript overrides the following browser APIs:
 ## Disclaimer
 
 This userscript is for personal use. Use at your own risk.
+
+## Discord
+
+Join the discussion: <https://discord.gg/C2baQRZUCW>