Add MA0211 to enforce multi-line XML documentation comments

[Copilot]

This adds a complementary rule to MA0177 for teams that want XML documentation comments to always use multi-line formatting, even when the content fits on a single line. The new rule is disabled by default so it can be enabled selectively.

• New analyzer rule

  • Added MA0211 to report single-line XML documentation elements such as <summary> and <param> when they can be rewritten in multi-line form
  • Scoped the rule to simple text-only XML elements and intentionally skips nested XML content and CDATA, matching the existing MA0177 boundaries

• Code fix

  • Added a fixer that expands inline XML documentation into standard multi-line /// form
  • Preserves indentation, comment prefixing, and tag attributes while rewriting the element

• Tests

  • Added focused coverage for:
    • single-line <summary> and <param> elements
    • empty XML elements
    • non-diagnostic cases for already multi-line comments, nested XML content, and CDATA

• Rule metadata and docs

  • Added docs/Rules/MA0211.md
  • Regenerated rule listings and packaged editorconfig entries so MA0211 appears alongside the existing analyzer set

Example:

/// <summary>description</summary>
class Sample { }

// becomes

/// <summary>
/// description
/// </summary>
class Sample { }

[meziantou]

@copilot This should be reported. Skip the logic to find nested elements. Report all non-empty summary element that are single line.

Also, do not report other elements, only summary. Make sure to also update the rule title, description and documentation page

[Copilot]

Addressed in ef91285 and feaad1a. MA0211 now only reports single-line, non-empty <summary> elements, no longer skips nested XML/CDATA inside <summary>, and the rule title/description/docs were updated accordingly.