[CodeMirror] Smaller and faster future upgrade script

[azawawi]

At the time of this writing, all of CodeMirror 4.6 JavaScript editing component is included in Farabi6. And farabi6 is not utilizing/need all the modes or functionality of that package. It would be cool to do the following in a Perl 6 build script:

• Work on a ~/codemirror folder. It is assumed to contain the latest version to upgrade to
• Copy the lib, addon, ...etc that is needed in the current farabi6 installation
• Copy the modes that are supported in Farabi6. Weird modes to be excluded
• Remove cruft like index.html, test.html and test.js
• Copy the filtered codemirror package to $FARABI_GIT_FOLDER/lib/Farabi6/files/assets/3rd-party/codemirror-v4.6
• Copy the license file
• Copy a README to tell that this is version xyz with the modifications made.

[azawawi]

This issue is going to be closed and is going to be kept for as a wiki page

https://github.com/azawawi/farabi6/wiki/Upgrade-CodeMirror-Procedure