[Feature] Allow custom metadata in script installation window

[TFWol]

When installing a script for the first time from a website, I would like to edit (rather than only being able to view) prior to it being added.

It's already right there in front of you and saves needing to reopen the script to change it.

[tophf]

No, I don't think we should encourage editing remotely installed scripts.
@gera2ld?

[TFWol]

I typically remove things like icon URLs if they're pointing to a weird website I don't want to touch.
Especially since the connection happens right away whether or not the script is activated.

To alleviate concerns, maybe a setting in Options with it turned off by default?

[tophf]

I guess we can add an option to ignore script @icon

[gera2ld]

Maybe we can allow changes to custom metadata before confirming installation?

[TFWol]

That'd be useful. 99% of the changes deal mostly with those.

[6b6279]

Some kind of option to "fork" a script would be nice too: The userscript get installed, but @downloadURL is empty (so there is no coupling between the local copy of the script and upstream).

[tophf]

The next version will have an Edit button when installing the script to open the editor in the same tab after installing: