FIX: Path vars for Windows environment

[mmurrell-r7]

The previous released version does not execute properly in Windows machines. This PR implements necessary fixes to allow for an operational Windows installer and executable.

Bug:

• On start-up, the Electron BrowserWindow is initialized, rendering the built html, css, and js assets. The filepaths for these assets are passed to our custom awsaml:// protocol handler, which opens and renders the files. On Windows machines, these filepaths will most likely live in the C:/ drive. When the filepath is passed to our protocol handler as a URL - e.g. awsaml://C:/Users/theUser/Downloads/awsaml/build/index.html - the C drive's colon : is removed and the filepath is handled as awsaml://C/Users/theUser/Downloads/awsaml/build/index.html which causes an error due to the filepath not existing. The BrowserWindow is unable to render properly.

Fix:
baseUrl = new URL(`awsaml:///${path.join(__dirname, '/../../build/index.html')}`).toString();

• URL object normalizes the file path, which will fix issues with separator variation between OS (/ for POSIX, / or \ for Windows)
• Converting the URL path to a string prevents the colon from being stripped out when passed to the protocol handler

[anguyen-r7]

👍