Batch Add to Collection: Make the header style consistent & Remove invalid link class

[kellnerd]

First of all, I wanted to say that I really like your userscript because it finally gives me the possibility to enter my collections more efficiently. So far I have been post-poning this task until there would be a better way to add/move many items in one go and only added few items every now and then. Basically I thought that I would probably have to implement something like this myself one day 😅

Therfore I have immediately installed and tested this script and spotted two minor issues:

• The header cells for the checkboxes which are injected by the script look slightly different than the standard ones. I have changed them to use the same selectors which are used by MBS on artist and RG pages.
• Creating a new collection links to an internal page for which there should not be an "external link" icon, the "new tab" icon is sufficient. I have removed the invalid link class.

[kellnerd]

To report bugs or request features, open an issue with according labels.

I am not sure whether it is possible to set labels for users who do not have write access to the repo. Feel free to add the appropriate label and remove the redundant prefix from the title of the PR.

Edit: I see that you have added some commits in the mean time and now have partially addressed hthe header style issue yourself. Do you want me to rebase on master and remove the (collection) bit from the commit messages?

[y-young]

The header cells for the checkboxes which are injected by the script look slightly different than the standard ones

Yes, I noticed that and have fixed that just now. Anyway, thanks for your contribution, I'm glad to hear that you like this userscript, it also helps me a lot. :)