Add support for Repository Discussions

[xcorail]

Closes: #213

This PR adds support for repository discussions, with the following tools:

• list_discussions
• get_discussion
• get_comments
• list_discussion_categories

As there is no support for discussions in the GitHub go library, these tools use the GitHub GraphQL API

Alternatives

I considered using the REST API, but it's not officially supported yet and lacks some features such as category filtering and pagination, requiring post-treatments.

[Copilot]

Pull Request Overview

This PR adds support for GitHub Repository Discussions using the GraphQL API by introducing four new tools, updating the tool registry, and providing example scripts and documentation.

• Introduces list_discussions, get_discussion, get_discussion_comments, and list_discussion_categories tools
• Registers the new discussions toolset in pkg/github/tools.go
• Implements GraphQL-based handlers in pkg/github/discussions.go with full test coverage and updates to README.md

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
script/get-discussions	Added example Bash script for calling list_discussions
pkg/github/tools.go	Registered new “discussions” toolset
pkg/github/discussions.go	Implemented handlers for discussions and categories
pkg/github/discussions_test.go	Added tests covering listing, retrieval, and comments
README.md	Documented the new discussions tools

Comments suppressed due to low confidence (2)

script/get-discussions:1

• [nitpick] The script is named 'get-discussions' but invokes the 'list_discussions' tool; consider renaming it to 'list-discussions' for clarity.

#!/bin/bash

pkg/github/discussions_test.go:36

• Current tests for ListDiscussions don’t cover pagination parameters ('first' and 'after') or sorting behavior; consider adding test cases for these conditions.

func Test_ListDiscussions(t *testing.T) {

[xcorail]

Fix documentation to previous renaming