Merge pull request #30575 from backstage/rugvip/copilot

.github: add copilot-instructions

.github/copilot-instructions.md

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+This is a TypeScript project structured as a monorepo using Yarn workspaces.
+
+## Code Standards
+
+The following files contain guidelines for the project:
+
+- `/STYLE.md`: guidelines for code style.
+- `/REVIEWING.md`: guidelines for pull requests.
+- `/SECURITY.md`: guidelines for security.
+- `/docs/architecture-decisions/`: contains the architecture decisions for the project.
+
+## Development Flow
+
+Before any of these commands can be run, you need to run `yarn install` in the project root.
+
+- Build: There is no need to build the project during development, and it is verified automatically in the CI pipeline.
+- Test: Use `yarn test <path>` in the project root to run tests. The path can be either a single file or a directory, and be omitted to run tests for all changed files.
+- Type checking: Use `yarn tsc` in the project root to run the type checker.
+- Code formatting: Use `yarn prettier --write <path>` to format code.
+- Lint: Use `yarn lint --fix` in the project root to run the linter.
+- API reports: Before submitting a pull request with changes to any package in the workspace, run `yarn build:api-reports` in the project root to generate API reports for all packages.
+
+All changes that affect the published version of packages in the `/packages` and `/plugins` directories must be accompanied by a changeset. See the guidelines in `/REVIEWING.md` for information on how to write good changesets. Changesets are stored in the `/.changeset` directory. Breaking changes must be accompanied by a `minor` version bump for packages that below version `1.0.0`, or a `major` version bump for packages that are at version `1.0.0` or higher.
+
+Never update ESLint, Prettier, or TypeScript configuration files unless specifically requested.
+
+## Repository Structure
+
+See `/docs/contribute/project-structure.md` for a detailed description of the repository structure.