Implement adding a user to a list from their profile

[namelessGonbai]

Fix #6058　

Add it only when you are following the "Add or Remove from Lists" button on the menu of the account

and add it to the list along with the option of creating a new list on the new ListAdder Modal screen created referring to ListEditor.

ListAdder's name is miserable, but I had no sense of naming. Also, since there is no experience of CSS or HTML <div> structure, I am worried about whether I could do it properly.

I used Javascript and css for the first time as I really wanted this function.
I tried as much as I could but please let me know if there is any problem.

[namelessGonbai]

need to fix css?
Do I need close this PR?

[Gargron]

You need to:

1. Remove trailing whitespace from the css file
2. Replace hardcoded hex color values with SCSS variables defined in variables.scss (with darken/lighten, see how it's done in other components)

[namelessGonbai]

・・・Error？Why？

[Gargron]

Seems unrelated to you, the 2.5 ruby tests passed.

[Gargron]

Is there any chance you can take a screenshot and put it in the description?

[namelessGonbai]

I skipped the word " in the description" and was delayed in fixing it.

[namelessGonbai]

Did you have any problems with this patch?