Update issue-fields-migration skill description

[labudis]

Updates the skill description and intro section to:

• Clarify support for both label migration and project field migration
• Add trigger prompts: "migrate my labels to issue fields", "migrate project fields to issue fields", "convert labels to issue fields", "copy project field values to issue fields"
• Introduce the issue fields feature with context on what it replaces and the default fields every org gets
• List the two migration sources (repo labels, Project V2 fields) with brief descriptions

[Copilot]

Pull request overview

This PR updates the issue-fields-migration skill's description and intro section to better reflect its dual migration capabilities (repo labels and Project V2 fields), adds example trigger prompts, and introduces context about the new issue fields feature.

Changes:

• Updated the description front matter in SKILL.md to clarify both migration sources and add trigger prompts
• Rewrote the intro section with a link to the changelog announcement and structured bullet list of migration sources
• Synced the description in docs/README.skills.md to match the updated SKILL.md

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
skills/issue-fields-migration/SKILL.md	Updated description and intro section to cover both label and project field migration with richer context
docs/README.skills.md	Synced the skill table entry description to match the updated SKILL.md