feat: add MailPit support #476

[prom3theu5]

This pull request adds support for a MailPit integration, including unit tests.

Documentation has been created under the PR: dotnet/docs-aspire#2633

This fulfils the proposal outlined in #476

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• New integration
  • Docs are written
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions

[prom3theu5]

@dotnet-policy-service agree

[aaronpowell]

Integration looks all good. @prom3theu5 are you willing to be added as the CODEOWNER of the integration?

[prom3theu5]

Hi @aaronpowell
Yeah sure thats fine

[aaronpowell]

Invite sent