Allow entry points to be other file types

I am using `fable-loader` to load `.fs` and `.fsproj` files. My entry point is an `fsproj` file. Unfortnately, I only get the following error when running `electron-webpack dev`:

`Error: Cannot find entry file src\Main\index.ts (or main.ts, or app.ts, or index.js, or main.js, or app.js)`

It seems the files to look for is hardcoded. This seems to put a complete stop to using arbitrary loaders for entry points in other formats/languages such as F# using `fable-loader`. (Sorry if this is nonsense; I'm very new to JS and webpack.)

Would it be possible to add support for specifying entry points of arbitrary names/extensions using configured loaders?