doc: Fix Markdown doc markup issues

[wenzeslaus]

While the documentation is still build from HTML files. Markdown files are now in the source code and needed additional modifications (#5057, #5064). Feel free to grab a small issue or your favorite tool, and fix what is needed.

Identifiable by a text search:

• Turn what was originally dt into headings or item lists as needed. (See where dt is in the .html file, fix the corresponding .md file.)

Identified by Markdown linting (delete the line from .markdownlint.yaml and fix what is needed):

• no-duplicate-heading docs: fix markdown linting issues heading-increment and no-duplicate-heading #5116
• heading-increment docs: fix markdown linting issues heading-increment and no-duplicate-heading #5116
• no-alt-text docs: fix no-alt-text #5154
• line-length docs: fix line-length #5174 (but keeps long lines in code and tables)
• no-emphasis-as-heading
• link-fragments
• no-space-in-links
• no-inline-html docs: fix no-inline-html (span tag only) #5148, docs: fix remaining no-inline-html #5149

Harder to identify:

• Basically all images need a human review. Some regular expressions may help with targeting the right files. [Bug] Conversion of HTML manual pages to markdown fails for HTML figure code #4864
• Some portion of the code blocks is wrongly assigned "sh" as a language. The HTML documentation did not distinguish languages, so sometimes the code blocks are text, sometimes Bash (specifically), Python, JSON, and maybe others. Searching for words Python and JSON is the first step. Tools with textual outputs and inputs should be second. [Bug] docs: remaining issues with markdown manual using mkdocs #4748

Additional issues:

• WARNING - Doc file 'imageryintro.md' contains a link 'band_references_scheme.png', but the target is not found among documentation files.
• INFO - Doc file 'r.mapcalc.md' contains a link 'rasterintro.md#raster-format', but the doc 'rasterintro.md' does not contain an anchor '#raster-format'.

Additional info

The nice thing about Markdown is that many tools including GitHub can display it (or you even don't have to). If you want to build the resulting documentation anyway, see #5048.

The mkdocs build has some issues too. They are tracked in #5058.

The deployment of mkdocs and Markdown files for grass-addons are not yet tracked in separate issues.

[echoix]

That sounds like some stuff I could try tomorrow, instead of making pytest work on grass-addons..

[wenzeslaus]

Cool. This is done. If you see issues with the syntax or how it is rendered, please fix or report.

Issue in addons for the same stuff:

OSGeo/grass-addons#1333