Help popup improvements

[jakubbortlik]

Bug Description

1. Every help popup created by gitlab.nvim also shows the line: ✎ = draft; 󰌸 = unlinked comment; ✓ = resolved. This should only be shown when the help is opened from the discussion tree. This can be easily fixed by adding a parameter the the help.open() function, so it could be a good first issue.
2. Every help on a gitlab.nvim popup contains the same information: ZA: Perform linewise action, ZZ: Perform action. This is not very helpful as the actions can be very different depending on the given popup/field. This information can be found in the plugin's help page, but a more informative info in the help popup would certainly be useful. This would require more work on the set_popup_keymaps function.