feat(developer/ide): Touch Layout > Export Platform Layers

### Is your feature request related to a problem? Please describe.

Reviewing a list of touch keyboard layers can be tedious when there are tens of layers to go through that must be selected one-by-one from the "Layer" menu. A quicker means to review all layers is highly desirable.

### Describe the solution you'd like

A KMD feature to export all layers into a single file would provide a global overview that would be useful to help spot a single layer that is different from the others and in need of an update. The web-based mobile keyboard tester has much of the capability needed already. The web tester presents a view of a single layer at a time in a web page, it could be adapted to present all layers at once, one after the other in a long list.

Two approaches then, (1) KMD could have an "export" feature that saved an HTML file with the list of layers, and references appropriate CSS files. (2) The web tester could have a menu option to "Show all layers" that then generated the list.

The displayed list of layers do **_not_** have to be functional, just the view is desired. Also, it is desirable to only show one device platform at a time as is currently selected, not for each device type on a single page.

### Describe alternatives you've considered

_No response_

### Related issues

_No response_

### Keyman apps

- [ ] Keyman for Android
- [ ] Keyman for iPhone and iPad
- [ ] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [X] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

16.0.139

### Operating system

Windows 11

### Device

Any

### Target application

N/A

### Browser

N/A

### Keyboard name

Any

### Keyboard version

Any

### Language name

Any

### Additional context

_No response_