bug: Modify stable url for keyboard download to exe and js files

[darcywong00]

From review comment #475 (review) for addressing #474

Hmm, is this (.htaccess) a much older bug, not actually coming out of the Apache/docker transition? Let's make sure we get it right for all patterns. The bundled installer .exe is now actually not a "bundle" but a file name pattern which causes the bundle to download (see https://kmn.sh/kb35, keyman-setup filename patterns section), so we may need to do some more work to get that right.

TODO:

• Fix download-exe
  For .exe, look at the pattern generated e.g. by https://keyman.com/keyboards/install/khmer_angkor, and use that: https://downloads.keyman.com/windows/stable/17.0.331/keyman-setup.khmer_angkor.exe

• Fix download-js
  download-js should go to downloads.keyman.com/keyboards/name/version/name.js, e.g. https://downloads.keyman.com/keyboards/thamizha_bamini/2.2/thamizha_bamini.js