docs: update README with project vision

[Copilot]

Resolves #1

Replaces generic plugin template README with approved project documentation for Copilot Small Task Automation.

• Project overview: Describes automatic Copilot assignment for issues with small time estimate labels
• How it works: Time label parsing, threshold comparison, GraphQL API integration
• Configuration: YAML example with upperLimitLabel setting
• Examples table: Label scenarios showing which trigger assignment vs skip
• Requirements: Copilot coding agent, GitHub App permissions
• Development: Local run commands and test instructions

Original prompt

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This section details on the original issue you should resolve

<issue_title>Update README with project vision</issue_title>
<issue_description>I've made a first draft, it's be approved so let's update it and start fleshing out issues to build things.

Copilot Small Task Automation

Automatically assigns GitHub Copilot to issues labeled with small time estimates. Perfect for automating quick tasks that don't warrant the overhead of manual assignment.

How It Works

When an issue is labeled with a Time: label, this plugin:

1. Parses the time duration from the label (e.g., Time: <1 Hour → 1 hour)
2. Compares it against the configured upperLimitLabel threshold
3. If the label's time is at or below the threshold, assigns Copilot to the issue

This uses GitHub's GraphQL API with the issues_copilot_assignment_api_support feature flag.

Configuration

plugins:
  - name: copilot-small-task-automation
    id: copilot-small-task-automation
    uses:
      - plugin: <plugin-url>
        with:
          # Any "Time:" label at or below this threshold triggers Copilot assignment
          upperLimitLabel: "Time: <1 Hour"

Examples

With upperLimitLabel: "Time: <1 Hour" (default):

Label Applied	Duration	Action
Time: <15 Minutes	15m	✅ Assigns Copilot
Time: <1 Hour	1h	✅ Assigns Copilot
Time: <2 Hours	2h	❌ Skipped (exceeds limit)
Time: <4 Hours	4h	❌ Skipped (exceeds limit)
Priority: High	N/A	❌ Skipped (not a time label)

Supported Label Formats

Labels must follow the format Time: <duration> where duration can be:

• 15 Minutes, 30 Minutes
• 1 Hour, 2 Hours, 4 Hours
• Any format supported by the ms library

Requirements

• Copilot coding agent must be enabled in the repository
• The GitHub App must have the following permissions:
  • Read access to metadata
  • Read and write access to issues and pull requests

Development

Running Locally

bun install
deno task dev:deno | bun dev:bun 

The worker runs on http://localhost:4000/

Testing

bun test

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Update README with project vision #1

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