(windows) Add .jsproj as file extension for XML files to ConfigFile

[holyhoehle]

Platforms affected

Windows

Motivation and Context

Fixes #62

Description

Added the file extension .jsproj to the allowed extensions for XML files in order to modify such files using the config-file tag in the config.xml

Testing

1. Add the following markup to the config.xml inside the <platform name="windows"> tag:

<config-file parent="/Project/PropertyGroup" target="CordovaApp.Windows10.jsproj" versions="10">
    <Test>Hello</Test>
</config-file>

2. Run cordova build windows

Result without this change:
The build is aborted with the error message: malformed document. First element should be <plist>

Result with this change:
The build completes without errors and the <Test>Hello</Test> Tag is written to the CordovaApp.Windows10.jsproj file.

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[erisu]

👍