HDDS-15260. Escape more elements in xml_to_md.py

[sarvekshayr]

What changes were proposed in this pull request?

Docusaurus build fails for update with <= in config property's description:

"Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`"

There may be other characters or patterns to escape.

Escapes characters (&, <, >) in addition to the existing {...} placeholder sanitisation to prevent MDX/JSX parsing errors in config values and descriptions.

What is the link to the Apache JIRA

HDDS-15260

How was this patch tested?

Configurations.md generated from CI.

| Minimum fraction of volume capacity reserved for local enforcement: writes fail when available space would drop below max(this ratio * capacity, `hdds.datanode.volume.min.free.space`). Should be <= min.free.space.percent so SCM can plan for a larger headroom than the DN enforces locally. |

Rendered view

[adoroszlai]

Thanks @sarvekshayr for the patch.