This makes gmnhg encode link destinations before rendering them into
Gemtext according to RFC 3986. This particularly fixes spaces in links.
Invalid URIs will skipped from rendering entirely.
Fixes#49.
This implements a Markdown / Gemtext suite, testing the entire renderer
at complex Markdown documents, containing the entirety of current
Markdown features accessible with gmnhg. The test suite can be expanded
by adding a pair of .md/.gmi files.
Minor bug fixes in JSON/Org metadata parsing where bugs were detected
with the test suite are also included in this patch.
Fixes#13.