feat(transformers): add support for [!code info] notation

[Divyapahuja31]

• -

Description

This PR adds support for [!code info] notation to transformerNotationErrorLevel.

What:
It extends the supported notations ([!code error], [!code warning]) to include [!code info]. Lines marked with this notation will be wrapped in a span with the classes highlighted info.

Why:
This allows users to highlight lines as informational notes in their code snippets, distinct from errors or warnings, which is common in documentation and tutorials.

Changes:

• Updated notation-error-level.ts to include the info class map.
• Updated documentation to include usages of [!code info].
• Updated test fixtures to include an example of [!code info].

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.25%. Comparing base (49cbb76) to head (719eb58).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1237   +/-   ##
=======================================
  Coverage   95.25%   95.25%           
=======================================
  Files          92       92           
  Lines        8007     8008    +1     
  Branches     1705     1704    -1     
=======================================
+ Hits         7627     7628    +1     
  Misses        374      374           
  Partials        6        6           

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