Add support for filtering the shop contents

[errnoh]

Goal is to merge functionality from the userscript based shop filtering into this extension. Still need to figure out things like how to easily configure filter rules, allow sharing/copypasting rules, have toggleable options, etc.

[errnoh]

I feel like we could do a text field configuration option where people can copy/paste filter definition similar to the ones currently being used. That would allow easy sharing of filter lists (bad part: shifts game towards "meta builds" instead of personal preference) which seems to be a common request people have.

[errnoh]

@danreeves multiple questions as I'm rather certain most of this is rather unidiomatic :)

• I do have to rename almost everything, but apart from that do you feel like the code is even remotely in the correct location?
• Is there a way to refresh the shop contents when the script is saved? (instead of having to jump to another character or refresh the page)
• And of course feel free to point out any other weirdness / stupid things.

(In addition there are still some issues in the filtering logic itself and I need to add some persisting toggles for the filtering functionality)

[errnoh]

Almost there. Only need to get configuration to persist for rest of the options, maybe find a way to clean some parts a bit and redo some of the naming.

[errnoh]

Hmm, functionality is there, naming is a bit less confusing and all options persist. Removing WIP label.

[errnoh]

So, I guess the questions now are:

• Should the filter rule textarea be based on screen size? Any suggestions?
• Any other cleaning that should be done?

[danreeves]

@errnoh just fyi i merged the melks store update so there are some conflicts here now