docs(developer): update with changes to v17

[mcdurdin]

From https://github.com/keymanapp/keyman/wiki/Keyman-17.0-Release-Notes (as of today):

• BREAKING kmcomp will be removed and replaced with kmc in 17.0 (#9158)
  • TODO: transition guide
  • TODO: documentation
  • kmc is now available as an NPM package in alpha (#8954)
• BREAKING .keyboard_info files are now generated entirely from the package and keyboard files. Extra fields are available in packages for license file, welcome file, typing examples, related packages (including deprecated packages), additional font files (#9485)
• BREAKING Keyboard and Lexical Model repositories have new build scripts (lm#226, kbd#2393)
• &displayMap allows keyboard developers to specify a font mapping to PUA for the On Screen Keyboard and Touch Layout to resolve diacritic rendering issues (#9032)
• Update to Unicode 15.1 (#9555)
• Added non-printing characters (#9846)
• Virtual keys in output of rules have never worked properly or been officially supported; Keyman Developer will now warn if you attempt to use this pattern (#10062)