Update all gzip-compressed tarballs to have a tar.gz extension

[mjang]

New style guide entry

We've just released more details in our style guide for the preferred file extension for "tarballs"

We have 34 files as of this writing with .tgz extensions

• Change them to tar.gz.
• Limit the change to Markdown files
  • Sometimes, packages are downloaded with the .tgz, especially in JSON files. Keep those .tgz files as is.
• Reviewer should make sure to check -- example, if there's a download, it might still appear as a tarball with a .tgz extension.

[Dindihub]

Hi @mjang can I be assigned this one? Thanks

[mjang]

Hi @mjang can I be assigned this one? Thanks

Hi @Dindihub , I look forward to your contribution!