Add CONTRIBUTING.md and GitHub issue/PR templates

[ZLeventer]

What does this PR do?

Adds community infrastructure so contributors know how to set up, write skills, and submit PRs.

Type of change

• Documentation

Skills affected

None — this adds repo-level docs only.

ZoomInfo tools used

N/A

Testing

N/A — documentation only.

Entitlements required

None.

Changes

CONTRIBUTING.md — includes:

• Prerequisites (Claude Cowork account + ZoomInfo API access)
• Project structure overview
• Skill authoring guide: anatomy of a SKILL.md, all available MCP tools, the lookup-first pattern, best practices for input handling / output formatting / fallback paths / data quality signals
• Guidance on adding new skills vs. improving existing ones
• Versioning convention

.github/ISSUE_TEMPLATE/bug_report.md — structured bug report template with ZoomInfo-specific context fields (API access, entitlements)

.github/ISSUE_TEMPLATE/feature_request.md — feature request template that captures use case, ZoomInfo tool involvement, and entitlement requirements

.github/pull_request_template.md — PR checklist covering skill directory naming, frontmatter, lookup-first pattern, output format, and testing confirmation

Checklist

• Skill directory name matches the name field in SKILL.md frontmatter
• description in frontmatter is clear and action-oriented (shown in Cowork UI)
• Skill uses the lookup-first pattern before any search call
• Output format is explicitly defined with markdown table headers
• Fallback paths are specified for no-match cases