fix: added "application/octet-stream" to the "stl" mime type in the Mimes config class

[Franky5831]

Description
I added the "application/octet-stream" to the "stl" mime type in the Mimes config class because when I upload a stl file the mime type returns as "application/octet-stream" and the ext_in input validation returns false.
I opened this issue and have been told to create a pull request.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[mergeable]

Hi there, Franky5831! 👋

Thank you for sending this PR!

We expect the following in all Pull Requests (PRs).

• PRs must be sent to the appropriate branch
• All git commits must be GPG-signed
• Must follow our style guide
• Be commented in the PHP source file
• Be documented in the user guide
• Be unit tested
• Pass all checks in GitHub Actions

Important

We expect all code changes or bug-fixes to be accompanied by one or more tests added to our test suite to prove the code works.

If pull requests do not comply with the above, they will likely be closed. Since we are a team of volunteers, we don't have any more time to work
on the framework than you do. Please make it as painless for your contributions to be included as possible.

See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md

Sincerely, the mergeable bot 🤖

[Franky5831]

Hey, I noticed the commit was unverified, I just added my GPG key and my commits are now verified, what should I do? Should I close it and do it over again?
Thanks for your time and patience.

[samsonasik]

you can do push --force, better to create different branch first tho so you can have easy on sync on future PR, see https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md#how-to-guide