[Feature] Add new item label to repeatable field

[mauricewijnia]

Adresses #3007

This adds the ability to change the text in the 'New item' button for the repeatable field

[welcome]

BOOM! Your first PR with us, thank you so much! Someone will take a look at it shortly.

Please keep in mind that:

• if this constitutes a breaking change, it might take quite a while for this to get merged; we try to emulate the Laravel release cycle as much as possible, so developers can upgrade both software once; this means a new big release every ~6 months;
• even if it's a non-breaking change, it might take a few days/weeks for the PR to get merged; unless it's a no-brainer, we like to have some community feedback on new features, before we merge them; this leads to higher-quality code, in the end; we learnt this the hard way :-)
• not all PRs get merged; sometimes we just have to hold out new features, to keep the packages lean; sometimes we don't include features that only apply to niche use cases;
• we're not perfect; if you think we're wrong, call us out on it; but in a kind way :-) we all make mistakes, best we learn from them and build better software together;

Thank you!

--
Justin Case
The Backpack Robot

[scrutinizer-notifier]

The inspection completed: No new issues

[tabacitu]

Perfect!

[tabacitu]

Totally agree! Thank you @mauricewijnia , merging right now into master. It'll be available with a composer update later today when we tag it.

Cheers!

[welcome]

WHOOP-WHOOP! Congrats, your first PR on this repo has officialy been merged.

You should also receive an email inviting you to the Community Members team. That's where we, commited community members, debate new features and decide what's in the Backpack roadmap. Feel free to ignore the invitation if you're not interested :-)

If you want to help out the community in other ways, you can:

• give your opinion on other Github Issues & PRs;
• chat with others in the Gitter Chatroom (usually for quick help: How do I do X);
• answer Backpack questions on Stackoverflow; you get points, people get help; you can subscribe to the backpack-for-laravel tag by adding a new filter; that will send you emails when new questions come up with our tag;

Again. Thank you for the PR. You are a wonderful person. Keep 'em coming :-)
Cheers!

--
Justin Case
The Backpack Robot

P.S. Help in the Backpack community is rewarded with free Backpack commercial licenses. It's the least we can do. If you feel you've helped the community with PRs, help & other stuff, please apply for free licenses and mention this PR. You scratch my back, I scratch your back. Thank you!

[dividy]

Had the same idea.

Thanks!