Support highlighting multiple ranges of source lines

Currently Gitlab supports highliting a source line through URL fragment - for example https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/initializers/load_balancing.rb#L9-11.

I'd like Gitlab to support highlighting multiple ranges of source lines. Extending the example above, the hypotnentical URL https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/initializers/load_balancing.rb#L9-11,L29-33 will highlight two discontinuous ranges, 9-11 and 29-33. This is particularly useful in project documentation where we'd like to call attention to specific, related, lines that are of interest.

Bitbucket already supports this feature (see https://bitbucket.uconn.edu/projects/AURORA/repos/wordpress-central-configuration/browse/.s2i/bin/assemble#7-12,22-26). The UI supports selecting multiple ranges via the standard combinations of Shift and Ctrl.

Background: at work, we're migrating from Bitbucket to Gitlab. Now, having migrated to Gitlab, our links are rather broken.