refactor: migrate from submodules to multi-root workspace for plugins (#198)

* refactor: migrate from submodules to multi-root workspace for plugins

- Updated LEDMatrix.code-workspace to include all plugin repos as root folders
- Removed symlinks from plugin-repos/ and plugins/ directories
- Updated .gitignore to reflect new plugin management approach
- Added setup_plugin_repos.py script for managing plugin symlinks (if needed)
- Added MULTI_ROOT_WORKSPACE_SETUP.md documentation

Plugins are now managed as independent repositories via multi-root workspace,
allowing for easier development and independent updates without modifying
the LEDMatrix project structure.

* Fix MULTI_ROOT_WORKSPACE_SETUP.md and add JSON error handling

- Remove deprecated clone_plugin_repos.py command reference
- Add language tag to directory tree code fence (fixes MD040)
- Add JSONDecodeError handling in setup_plugin_repos.py with user-friendly error messages

---------

Co-authored-by: Chuck <chuck@example.com>

.gitignore

@@ -35,29 +35,8 @@ htmlcov/
 # Cache directory (root level only, not src/cache which is source code)
 /cache/
 
-# Development plugins directory (contains symlinks to plugin repos)
-# Plugins are installed via plugin store, not bundled with main repo
-# Allow git submodules
+# Development plugins directory
+# Plugins are managed as separate repositories via multi-root workspace
+# See docs/MULTI_ROOT_WORKSPACE_SETUP.md for details
 plugins/*
 !plugins/.gitkeep
-!plugins/odds-ticker/
-!plugins/clock-simple/
-!plugins/text-display/
-!plugins/basketball-scoreboard/
-!plugins/soccer-scoreboard/
-!plugins/calendar/
-!plugins/mqtt-notifications/
-!plugins/youtube-stats/
-!plugins/olympics-countdown/
-!plugins/ledmatrix-stocks/
-!plugins/ledmatrix-music/
-!plugins/static-image/
-!plugins/football-scoreboard/
-!plugins/hockey-scoreboard/
-!plugins/baseball-scoreboard/
-!plugins/christmas-countdown/
-!plugins/ledmatrix-flights/
-!plugins/ledmatrix-leaderboard/
-!plugins/ledmatrix-weather/
-!plugins/ledmatrix-news/
-!plugins/ledmatrix-of-the-day/