Merge PRs GorvGoyl#78, GorvGoyl#88, GorvGoyl#90\n\n- Fixes PR integration conflicts\n- Migrates extension icons to standard VSCode codicons (GorvGoyl#90)\n- Adds new fold/unfold + PlantUML buttons (GorvGoyl#78)\n- Adds toggle maximize editor group button (GorvGoyl#88)\n- Sets activationEvent properly to onStartupFinished to correctly load up the extension on new versions of VSCode.

Co-authored-by: thexmeta <3031096+thexmeta@users.noreply.github.com>

Author: google-labs-jules[bot]