Add slash commands for selected issues on issue boards

I think it would make for a powerful workflow if it was possible to apply slash commands to the selected issue on issue boards without opening it. An sample workflow could look like this:

1. Navigate to issue either by clicking or using shortcut keys (if implemented, see https://gitlab.com/gitlab-org/gitlab-ce/issues/40062)
2. Press Ctrl + / to bring up a single line command prompt.
3. Type in a slash command followed by Enter

After pressing enter, the issue would be updated and the sidebar menu would immediately reflect this. This could greatly facilitate organizing, and assigning weight/time estimates to issues in big projects quickly, since it is faster than opening up each issue individually to modify it. Often the sidebar contains all the relevant information to assign labels, time estimates weights, etc.