Adds issue template for the plugin release process

[ryanwelcher]

What?

This PR introduces a new issue template for the Gutenberg release process based on #49210

Why?

By having a template, we take the guess work out of the process and make it more public and easier for others to do.

[ryanwelcher]

@justintadlock I made a few changes to the release day steps and added info about running the workflow based on our experience this week

[justintadlock]

It mostly looks good to me. I like the addition of the links to the guide for publishing a release added in the steps.

I wonder if we should do something like ADD_LINK instead of linking to the 15.4 Google Doc. On the other hand, it might not hurt to leave that example in place.

[ryanwelcher]

It mostly looks good to me. I like the addition of the links to the guide for publishing a release added in the steps.

I wonder if we should do something like ADD_LINK instead of linking to the 15.4 Google Doc. On the other hand, it might not hurt to leave that example in place.

I'd say we leave it as an example for now and go from there.