Match <!--more--> in addition to <!-- more -->

[clarfonthey]

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Are you doing the PR on the next branch?

I noticed this when trying to migrate a few WriteFreely posts to Zola. WriteFreely uses <!--more--> when added via the rich-text editor, whereas Zola was picky about the spaces around the tags. I replaced the check with a regex so that spaces and case don't matter any more.

[Keats]

Can you add a test?

[clarfonthey]

Sorry for taking a bit to get to this-- a lot of my focus was on trying to get my particular static site setup working, and I was just submitting PRs for the changes I made that I thought would be reasonable to upstream.

I added some tests directly to the markdown parser, since it seems that most of the current summary-splitting tests are in the content itself. This way, it's a little closer to a unit test than an integration test.

Unfortunately, newline-split <!-- more --> would not work under this setup due to the way pulldown-cmark works, and I filed a bug to see if upstream would be interested in fixing this. But at least for now, allowing extra spaces between the more tags, and case-insensitivity, seems like a net improvement.

I also apologise that the test code is a little weird, adding in trims instead of detecting newlines between paragraph tags, but I figured that this would be more resilient in case the parser were to change to remove those.