Make it easier to add a story

[llewelld]

Adds "Add Story" buttons to various places.

Adds a process diagram to the registration page to try to clarify what the user needs to do to register an accont.

Fixes #599.

[github-actions[bot]]

Coverage report

The coverage rate went from 98.79% to 98.79% :arrow_up:

100% of new lines are covered.

Diff Coverage details (click to unfold)

### server/apps/main/tests/test_views.py `100%` of new lines are covered (`99.09%` of the complete file). ### server/apps/main/views.py `100%` of new lines are covered (`97.25%` of the complete file). ### server/apps/users/tests/test_views.py `100%` of new lines are covered (`100%` of the complete file).

[llewelld]

I'm happy to wait for #631 to go in first.

[gedankenstuecke]

Okay, I think I wrapped up all open work on #631 for now, let's get that in and then this one!

[gedankenstuecke]

As feared, there's now some merge conflicts. @llewelld are you happy for me to try to resolve those? 😄

[llewelld]

@llewelld are you happy for me to try to resolve those? 😄

Thanks for the offer. I still have the code on my machine and some lingering context in my head, so I'd be keen still to do this.

[gedankenstuecke]

That’s why I asked, I didn’t want to snatch away the work - but also don’t want you to feel obliged to do it! ☺️

[llewelld]

I appreciate you asking! I wouldn't have wanted this to block progress, but equally I'd feel uncomfortable not finishing the task.

I've fixed the conflicts. I think I caught all of the Bootstrap 5 changes, but I may have missed some. Please do flag them up if you spot any.

[llewelld]

Thank you @gedankenstuecke!