From the 2 marketplace links you linked above, click "Download Extension" on the right side of the page. Rename that file from .vsix to .zip then extract the zi

From the 2 marketplace links you linked above, click "Download Extension" on the right side of the page. Rename that file from .vsix to .zip then extract the zip file to get a folder containing the source files for the extension. It's not as readable as if they published open source on GitHub, but you can still see what the extension is doing.