Set Content-Type in issueBulkOperations.submitBulkTransition to work around api issue

[Cellule]

Fixes #374

[MrRefactoring]

It would be wonderful if you could write an integration test case

[Cellule]

I didn't see any tests for other bulk operations so I wrote a new test file
I didn't actually run the integration test, I'm not really setup for it right this moment and I'm not sure I want to run this against my company jira instance
If there are problems I could look at setting up locally to run integration tests
Edit: I created a personal jira instance to run the tests and everything looks good. I've also confirmed that the test fails if I comment out the Content-Type fix

I also noticed the typescript config wasn't picking up the tests files causing a whole bunch of errors in IDE so I fixed that
Then I noticed the tests files weren't compiled in CI so I added that and fixed the build
Let me know what you think

[MrRefactoring]

I’ll merge your changes to test more thoroughly and may make some adjustments

[MrRefactoring]

I took a closer look, and it’s excellent work—you’re a total brainiac to catch a problem like this!

[Cellule]

I took a closer look, and it’s excellent work—you’re a total brainiac to catch a problem like this!

Hahaha thanks, I was pretty deep down the rabbit hole and I'm trying to crawl out of it slowly XD
Can't wait to use it in my project!