[Feature request] Support to make neovim numhl of sign fade.

[kevinhwang91]

I saw some code in signs.py about linehl were commented.

      # linehl adds high performance hit -- maybe add toggle for this
      # if 'linehl' in item:
        # linehl_id = vim.eval('hlID("'+item['linehl']+'")')
        # if linehl_id:
          # ids.append(linehl_id)
        # definition += ' linehl=vimade_' + linehl_id

and numhl of sign works after I added below code.

      if 'numhl' in item:
        numhl_id = vim.eval('hlID("'+item['numhl']+'")')
        if numhl_id:
          ids.append(numhl_id)
        definition += ' numhl=vimade_' + numhl_id

But it must make sure that the option checkinterval of vimade greater than the option updatetime of neovim, otherwise, vim-gitgutter enabled g:gitgutter_highlight_linenrs = 1 may works unexpected.

I don't know why, please support this feature with bug-free code.

[TaDaa]

Will get the issue you are talking about resolved, its been there in the back of my mind but I keep putting it off.

+1 for supporting numhl. I want to say linehl should be supportable at this point on neovim as well given all the highlighting performance improvements it currently has over vim -- will look into re-enabling it.

[TaDaa]

linehl and numhl should now be supported with some perf improvements and logic for sign prioritization.

Currently considering options to catch signs that might be triggered off of updatetime -- likely will update vimade to consult both signsretentionperiod and updatetime, which should handle most plugins without specific configurations. Should have an update on this one in a day or 2.