feat: <output> base directory support for relative paths

[fpelliccioni]

No description provided.

[cppalliance-bot]

An automated preview of the documentation is available at https://743.mrdocs.prtest2.cppalliance.org/index.html

[cppalliance-bot]

An automated preview of the documentation is available at https://743.mrdocs.prtest2.cppalliance.org/index.html

[alandefreitas]

CI failed. MRDOCS_ASSERT doesn't support two arguments. Did you run this locally?

[fpelliccioni]

CI failed. MRDOCS_ASSERT doesn't support two arguments. Did you run this locally?

the first commit was compiled and tested, including support for this parameter in ConfigOptions.json (local change, not pushed):

{
  "name": "tagfile-path",
  "type": "file-path",
  "default": "<output>/reference.tag.xml",
  "relativeto": "<output>",
  "must-exist": false
}

I sent the second commit without checking it—my apologies for that. I'll fix and re-test it.

[cppalliance-bot]

An automated preview of the documentation is available at https://743.mrdocs.prtest2.cppalliance.org/index.html

[cppalliance-bot]

An automated preview of the documentation is available at https://743.mrdocs.prtest2.cppalliance.org/index.html