Reconsider rewriting of files

[lastmjs]

Apparently the browser really doesn't care about file extensions, only mine types. This means we should be able to allow any extension to be requested by the browser. The only issue seems to be the TypeScript extension that disallows any file extension besides js. If mjs goes through in Node, then I'm hoping the TypeScript plugin will change and allow others file extensions. This would greatly simplify rewriting of file extensions.

https://medium.com/webpack/the-state-of-javascript-modules-4636d1774358

https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types

[lastmjs]

Follow these issues for more info:

microsoft/TypeScript#4595

microsoft/TypeScript#10939

angular/angular#14664

[lastmjs]

I still hope that eventually the Atom and Visual Studio code plugins will allow .ts extensions, because providing explicit extensions will be so much better. Once explicit extensions are allowed, get rid of the implicit extension handling