9 allow addition of arbitrary attributes to metadata profiles

[pmslavin]

This PR allows the addition of arbitrary json objects as "context attributes" with the -a/--context-attribute option and also merges in the documentation branch adding mkdocs support.

Tests are provided for command-line invocations using --context-attribute and documentation is extended to include this.

[Copilot]

Pull request overview

This PR adds a new CLI option for attaching arbitrary JSON “context attributes” into the generated metadata profile, and introduces an MkDocs-based documentation site (including GitHub Pages deployment support).

Changes:

• Add -a/--context-attribute to include a JSON object under metadata.attributes in CLI output.
• Add pytest coverage for CLI invocations using --context-attribute.
• Add MkDocs configuration/content, docs dependencies, and a GitHub Actions workflow for publishing docs.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 19 comments.

Show a summary per file

File	Description
tests/test_context_attribute.py	New CLI-focused tests for context attribute parsing/behavior.
setup.py	Adds docs extras with MkDocs-related dependencies.
mkdocs.yml	Adds MkDocs site configuration and navigation.
dsprofile/utils/fileops.py	Extends metadata generation to include parsed context attributes.
dsprofile/main.py	Adds new CLI flag and wires it into metadata generation; adds omit-metadata conflict check.
dsprofile/lib/reader.py	Tightens Reader subtype key validation (reject spaces) and adjusts docstring formatting.
docs/stylesheets/extra.css	Adds custom MkDocs Material styling.
docs/reference/utils.md	Adds mkdocstrings-based API reference page for utilities.
docs/reference/reader.md	Adds mkdocstrings-based API reference page for Reader.
docs/reference/index.md	Adds API reference section landing page.
docs/install.md	Adds installation instructions to docs site.
docs/index.md	Adds documentation home page.
docs/extending/reader.md	Adds developer guide for implementing new Readers.
docs/extending/index.md	Adds “Extending” section landing page.
docs/examples/output-config.md	Adds placeholder examples page.
docs/examples/index.md	Adds examples section landing page.
docs/examples/advanced-install.md	Adds advanced install/testing/docs build instructions.
docs/context-attributes.md	Adds documentation for the new context attributes feature and output format.
docs/cli.md	Adds CLI reference documentation including the new option.
README.md	Updates README usage snippets to include geopackage + context-attribute option and expands omit-digest info.
.github/workflows/mkdocs-to-gh-pages.yml	Adds a workflow intended to build/deploy docs to GitHub Pages.
.github/workflows/ci.yml	Renames workflow display name (“CI” → “Tests”).

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