Review HACKING docs

Specifically:
- abandon the FAQ layout for improved readability;
- remove sections describing issues which can be easily searched;
- add current priorities.
Add Youtrack Workflow Editor 5.2.1
Merge pull request #6374 from cafferata/youtrack-workflow-editor

Add Youtrack Workflow Editor 5.2.1
Add "网易云音乐" for Mac.
Adding Tal Chorus LX Audio Plugin, latest version.
Merge pull request #6380 from ndr-qef/PrismaPhonic-TalChorusLX

Adding Tal Chorus LX Audio Plugin, latest version.
Merge pull request #6376 from mingzhi22/netease-music

Add "网易云音乐" for Mac.
Merge pull request #6342 from ndr-qef/docs/hacking

Review HACKING docs
Revert "WIP Review HACKING docs"
Merge pull request #6383 from caskroom/revert-6342-docs/hacking

Revert "WIP Review HACKING docs"