chore(web): improve the KeymanWeb integration documentation
- replace use of `kmw` with `keyman`
- unify pattern to load keyboards: do it in `keyman.init().then()` instead of in the document `onload`
Part-of: keymanapp/keyman.com#449
The guide examples load `keymanweb.js` from the CDN, but the documentation
explaining the examples showed loading local file. This change adjusts
the docs to show loading from CDN.
Built-bot: skip
Test-bot: skip
- replace use of `kmw` with `keyman`
- unify pattern to load keyboards: do it in `keyman.init().then()` instead
of in the document `onload`
Part-of: keymanapp/keyman.com#449
Test-bot: skip
Note: build.sh updated to make sure that test:help build action:target
doesn't also call test.sh by adding `:_all` meta-target.
Note: CI will need a new help-keyman-com.sh build step to deploy web
engine help.
Fixes: #12347
