Provide interactive prompts to create fragments with the correct names

[chadrik]

As a developer, I'd like for towncrier to automatically generate the fragment file name so that I don't have to, and so that I don't make mistakes. To achieve this, towncrier create should prompt the user to input the necessary info using a library like itsprompt.

The series of prompts should be:

• unique id (or press enter to use timestamp)
• fragment type
• section (if they are configured)

This could be introduced in one of three ways:

• add a new flag to towncrier create, e.g. towncrier create -p
• change the default behavior of towncrier create
• introduce a new entrypoint, such as towncrier new

Take a look at the changie new portion of the changie mege animation here: https://changie.dev/guide/quick-start/

[adiroiban]

Happy to review and merge a PR for this.

I think that is ok to change the defaul behaviour of towncrier create

If you don't pass a FILENAME argument it will enter the new prompt/interactive mode.

[SmileyChris]

Implemented in #482