chore(core): move API docs from help.keyman.com

[mcdurdin]

Reorganizes /core/doc to /core/docs and moves internal files accordingly.

Depends-on: keymanapp/help.keyman.com#1684

@keymanapp-test-bot skip

[keymanapp-test-bot[bot]]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Android
  • Keyman for Android apk
  • FirstVoices for Android 16.0 apk
  • FirstVoices Keyboards for Android apk
  • KeyboardHarness apk
  • Keyman for Android 16.0 apk
  • KMSample1 apk
  • KMSample2 apk
• Developer
  • Keyman Developer
  • Compiler Regression Tests
  • kmcomp.zip
• iOS
  • Keyman for iOS (simulator image)
  • FirstVoices Keyboards for iOS (simulator image)
  • TestFlight internal PR build version - 18.0.136 (0.12642.12244)
• Keyboards
  • Test Keyboards
• Linux
  • Keyman for Linux: focal
  • Keyman for Linux: jammy
  • Keyman for Linux: noble
  • Keyman for Linux: oracular
• macOS
  • Keyman for macOS
• Web
  • KeymanWeb Test Home
• Windows
  • Keyman for Windows
  • FirstVoices Keyboards for Windows
  • Text Editor (32 bit)
  • Text Editor (64 bit)

[keyman-server]

Changes in this pull request will be available for download in Keyman version 18.0.138-alpha