build specific api files

[bumi]

based on the build this copies the request api that will be used in the JS app

[rolznz]

Downsides of this approach:

• accidentally editing request.ts and it making no changes and being overwritten if the build or dev mode is restarted
• hot reloading does not work for platform-specific files

But we probably will not make many more edits to this file.

The alternative would be a dynamic import using the value of an env variable (that was removed in this PR) as part of the filename of the imported file, which would not have the downsides mentioned above.

I will merge this for now, in the rare case that we end up adding more platform-specific code we could revisit it.