fix: Also render title in markdown template without name

[infinisil]

Description

Previously, if there was no project name defined, the default markdown template wouldn't render the title properly due to a missing #.

Checklist

• Make sure changes are covered by existing or new tests.
• For at least one Python version, make sure local test run is green.
• Create a file in src/towncrier/newsfragments/. Describe your
  change and include important information. Your change will be included in the public release notes.
• Make sure all GitHub Actions checks are green (they are automatically checking all of the above).

[adiroiban]

Many thanks for the changes.

They look good.

I left a few minor comments.

I hope we can have those improvemnets before the merge.

Thanks again!

[infinisil]

Great suggestions, thanks! Applied them :D

[adiroiban]

Thanks for your help. I have enabled auto-merge. I hope this will land soon.