Md2gemini

This bugfix release:
- Goes back to using CRLF (aka `\r\n`) for line endings, to ensure Windows support
- Respects markdown [hard line breaks](https://spec.commonmark.org/0.29/#hard-line-breaks), as it should - 18

This release adds the `--base-url` and `--md-links` options and auto removes fragment/hash links.

7 13 11

This releases adds the `--strip-html` option. It also remove inline HTML when `--plain` is used, and adds some extra newlines around blocks that should have been added before.

Fixes 8, so that image tags are actually added to image links - on the command line and through library usage.

Adds the `--frontmatter` option to support [Zola](https://www.getzola.org/) frontmatter. Now `--jekyll` is deprecated, but still works of course.

EDIT: Technically, this should have been release `v1.3.0`, my bad. I will leave it as is to not break any compatibility. I've retroactively added a `v1.3.0` git tag to this same commit, but I will leave PyPI as is.