Support blank space naming for filter dropdown
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=216192) </details> <!--IssueSummary end--> Currently adding spaces in the names of filter options is not possible. The solution thus far has been to add dashes `-` where spaces would exist. But this impairs readability and scanability of the filters list :slight_frown: ![image](/uploads/1b434b905c005b8c8369ef186761ffaa/image.png) ### Considerations 1. Using spaces today in the filter bar breaks the query ([example video](https://gitlab.com/gitlab-org/gitlab/uploads/351b9d3635e7d6cc8a4d6260279cc59f/Kapture_2020-04-30_at_17.45.41.webm)) 1. Make sure that old URLs, using the current `-` format still work. ### Relevant Files **The Magic 🎩** - https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/filtered_search/filtered_search_dropdown_manager.js#L160 - https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/filtered_search/filtered_search_token_keys.js#L52 - https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/filtered_search/filtered_search_manager.js#L734 **CE Labels using dashes** - "my-reaction" > https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/filtered_search/available_dropdown_mappings.js#L104 - "target-branch" > https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/filtered_search/available_dropdown_mappings.js#L138 **EE Labels using dashes** - "approved-by" > (not yet merged) https://gitlab.com/gitlab-org/gitlab/-/merge_requests/30335
issue