bug(loader): check for existing loader plugins when patching RequireJS

[EisenbergEffect]

The loader.js attempts to patch require.js by detecting all HTML files and prepending the module id with a custom loader plugin. However, it may be that files with an html extension have been explicitly required by the developer and aren't intended to be turned into view factories. To fix, detect whether the module id is already prepended by a loader plugin and bypass if it is.