docs: add local test data setup step

[samay2504]

This PR updates contributor guidance with a short local workflow for editable installation, dataset preparation, and test execution, and it explicitly documents running libpysal.examples.fetch_all() before tests so contributors avoid missing-data failures during local runs.

[Copilot]

Pull request overview

Updates contributor documentation to include a short local workflow that ensures required example datasets are available before running tests.

Changes:

• Adds a “Local development and tests” section describing editable install with dev extras.
• Documents pre-fetching libpysal example datasets via libpysal.examples.fetch_all() to avoid missing-data test failures.
• Provides a basic command to run the test suite locally.

---

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[Copilot]

These fenced code blocks are indented with hard tab characters. GitHub-flavored Markdown can render tabs inconsistently inside ordered lists, and this also introduces literal tabs into the file. Prefer indenting the fenced blocks with spaces (typically 4 spaces under the list item) and update the other two blocks similarly for consistent rendering.

Suggested change

	```bash
	pip install -e ".[dev]"
	```
	2. Download required example datasets before running tests:
	```bash
	python -c "import libpysal; libpysal.examples.fetch_all()"
	```
	3. Run the test suite:
	```bash
	pytest spopt/tests/
	```
	```bash
	pip install -e ".[dev]"
	```
	2. Download required example datasets before running tests:
	```bash
	python -c "import libpysal; libpysal.examples.fetch_all()"
	```
	3. Run the test suite:
	```bash
	pytest spopt/tests/
	```