Track status for feature "Extension constants"

[jcouv]

Adds feature status tracking row.

• csharplang issue: [Proposal] Extension constants csharplang#10242
• Test plan: Test plan for "Extension constants" feature #84269

FYI @jcouv

(created by new-compiler-feature skill)

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds a new entry to the Roslyn “Language Feature Status” tracking table for the C# feature Extension constants, so its proposal, working branch, test plan, and ownership are visible alongside other in-progress features.

Changes:

• Add a new “Working Set C#” table row for Extension constants.
• Link the row to the csharplang proposal issue, the features/extension-consts branch, and the Roslyn test plan issue.
• Record initial ownership fields (developer + LDM champ) and leave reviewer/IDE buddy as TBD.

Show a summary per file

File	Description
docs/Language Feature Status.md	Adds the “Extension constants” feature row to the in-progress C# tracking table with links to proposal/branch/test plan and initial ownership fields.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0