same as last PR but with user command

[BirdeeHub]

Added ability to get selection in visual mode

fixed bugs surrounding the presence of .git or not at the end of the link, as well as made it work correctly for oil:// type buffers for those who use the popular oil file manager

broke function up into 2 parts to ease adding of platforms besides github

removed hard errors, swapped them for prints. can be viewed with :messages if not rendered, or can be swapped back to hard errors

Added user commands and updated readme