adding default toolset

[tonytrg]

Closes:
Updated the help section to display all available toolset groupings

      --toolsets strings          Comma-separated list of tool groups to enable (no spaces).
                                  Default: context, users, repos, contents, pull_requests
                                  To enable all tools, use all
                                  Available: context, repos, contents, releases, issues, sub_issues, users, orgs,
                                             pull_requests, pull_request_reviews, code_security, secret_protection,
                                             dependabot, notifications, discussions, actions, security_advisories,
                                             experiments, gists, projects, stargazers, dynamic
  -v, --version                   version for server

[Copilot]

Pull Request Overview

This PR changes the default toolset configuration from "all" to a specific set of core tools and updates related documentation to reflect the new default behavior.

• Replaces the single "all" toolset with explicit core toolsets: "context", "repos", "issues", "pull_requests"
• Removes the "// indirect" comment from a dependency in go.mod
• Updates flag description to remove reference to "enabling all"

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pkg/github/tools.go	Updates DefaultTools from ["all"] to specific core toolsets
go.mod	Removes indirect comment from go-querystring dependency
cmd/github-mcp-server/main.go	Updates toolsets flag description to remove "all" reference

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

Removing the '// indirect' comment suggests this dependency is now being used directly, but there's no corresponding code change showing the direct usage. If this is indeed now a direct dependency, consider adding it to the non-indirect section of the dependencies or ensure the direct usage is properly reflected in the codebase.

Suggested change

	github.com/google/go-querystring v1.1.0
	github.com/google/go-querystring v1.1.0 // indirect