feat(developer): Incorporate standalone gestureChart tool into kmc

This incorporates @mcdurdin 's review comments originally from keymanapp/keyboards#2594

The gestureChart tool (moved to its own repo keymanapp/gestureChart) documents gestures in a touch layout as a Markdown table.

Remaining issues + integration involved:
- [ ] Don't need to support `T_ keys`
- [ ] Integrate this into kmc as a kmc module. Then we could merge it in 18.0.
- [ ] Special Markdown character replacement needs to be done on the whole string (currently won't work with `x|` or things like that). Use `escapeMarkdownChar` function in Developer
https://github.com/keymanapp/keyman/blob/5062bbad984760a40e5ee3d012b65d54d805db1d/developer/src/common/web/utils/src/markdown.ts#L2-L21
- [ ] Use `TouchLayoutFileReader` to read .keyman-touch-layout file because that does validation and normalization of content