Root Mounted paths, override output files

[AngelMunoz]

Describe the bug When we have root mounted paths, the build command copy features are overwriting the correct esbuild output files, this happens because we copy the contents of the mounted directories except F# sources while we normally don't care (because we use the .fs.js extension) when we're dealing with pure js files this can force wrong outputs.

While we usually exclude some of the files with build.excluides I think this is a fairly common scenario or one that at least we should be able to support

To Reproduce Steps to reproduce the behavior:

1. With a perla.json file like this:

   {
   "index": "./index.html",
   "mountDirectories": {
   "/": "./src"
   },
   "fable": {
   "extension": ".js"
   }
   }

   attempt to run perla build

2. the outDir directory is filled with the contents of src

Expected behavior While we should copy some of the contents of the mounted directory we should avoid copying the source code files to avoid override these situations.

Desktop (please complete the following information):

• OS: any
• Browser: any
• Version: v1.0.0-beta-012 and below

Additional context Found at #96

[AngelMunoz]

this was fixed but will close in favor of #128 for the remaining work