Try to get the `.editorconfig` and `.prettierrc` files as close as possible
to the formatting that was used in Flamenco. Because these files weren't
here during most of Flamenco's development so far, having them caused quite
a few changes in the webapp files.
No functional changes intended.
Brave (and maybe other browseres) refuse to set the 'User-Agent' header
in XMLHTTPRequests, and are vocal about this in the debug log. Since the
OpenAPI code generator always outputs a custom 'User-Agent' header, I've
added some JS code to strip that off when constructing an API client.
