Add language tag to code blocks and correct indented code block

[bact]

• Add language tag (like xml, json) to Markdown code blocks, so the code syntax will be properly highlighted in the document
• Fix indent of a code block nested inside a numbered list
• Fix other Markdown lint warnings. Like removing end-of-line trailing spaces and ensuring a blank line before and after a heading.

[bact]

Thank you for detailed suggestions. I have updated them accordingly.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.13%. Comparing base (acc6ab3) to head (ba9dc58).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #770   +/-   ##
=======================================
  Coverage   70.13%   70.13%           
=======================================
  Files         277      277           
  Lines        8651     8651           
  Branches     1006     1006           
=======================================
  Hits         6067     6067           
  Misses       2065     2065           
  Partials      519      519           

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