+librttopo

[JrGoodle]

closes #551

[what-the-diff]

PR Summary

• Added a new file: package.yml
  This PR introduces a new file named package.yml.
• Distributable URL
  The URL for the distributable is provided: https://git.osgeo.org/gitea/rttopo/librttopo/archive/${version}.tar.gz
• Version pattern matching
  The versions are found in tags and match the pattern of librttopo-\d+.\d+.\d+.tar.gz (e.g. 1 or more digits followed by . then 1 or more digits, etc.)
• Version number extraction
  The PR helps to extract just the version number (e.g. 2_0_1) from the tarball name (e.g. librrtoto-2_0_1) by stripping out the leading 'librtotpo-' and trailing '.tar'.