fix: prevent <button>'s from becoming form submit when they shouldn't

[dsevillamartin]

Changes proposed in this pull request:
Adds type=button to most <button> usage (except the AdminPage#submitButton). The first button of type submit (which is the default in HTML if undeclared) becomes what the enter keybind presses in a form. This makes the behavior with these components make more sense.

I found this behavior while trying to make an extension page use a

, and enter kept opening a dropdown way down the page. Even though I could've rectified this by implementing onsubmit, the submit behavior was already declared in the button (using AdminPage#submitButton) so there was no reason to if I could stop the dropdown from becoming the form's submit button.

Reviewers should focus on:
I believe all the buttons that were missing a type declaration (except the one in AdminPage, which I added just for clarity) should all be regular buttons. They can still be clicked by pressing enter when focused, but they won't override the submit button of a <form> if they're the first submit button anymore.

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
  • Did not test extensions, but just adding type="submit" and having the code compile should be fine.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Related documentation PR: (Remove if irrelevant)

[SychO9]

Thanks!