[snippet_var_resolver] Add plugin to resolve variables inside of snippets

[eshaben]

This pull request introduces a new MkDocs plugin, snippet_var_resolver, which resolves {{ variable }} placeholders in HTML content that remain after snippet injection, ensuring variables from YAML files are correctly rendered even when injected via pymdownx.snippets. The plugin is fully documented, registered in the project, and covered by comprehensive tests.

New Plugin: Snippet Variable Resolver

• Added SnippetVarResolverPlugin in plugins/snippet_var_resolver/plugin.py, which:
  • Loads variables from YAML files specified in the macros plugin's include_yaml config.
  • Replaces unresolved {{ variable }} placeholders in the HTML after snippet injection, supporting dotted paths and leaving unknown variables untouched.
  • Handles multiple YAML files, merging variables with "last file wins" precedence, and logs helpful debug/warning messages.

Documentation

• Created docs/snippet-var-resolver.md with usage instructions, configuration details, and notes about plugin behavior and limitations.

Project Registration

• Registered the plugin entry point in pyproject.toml under [project.entry-points."mkdocs.plugins"].
• Bumped the project version to 0.1.0a11 to reflect the new feature.

Testing

• Added tests/snippet_var_resolver/test_snippet_var_resolver.py with thorough unit tests for variable resolution logic, YAML loading, and integration scenarios.

[Copilot]

Pull request overview

Adds a new MkDocs plugin (snippet_var_resolver) to resolve leftover {{ variable }} placeholders in rendered HTML (after snippet injection), using variables sourced from mkdocs-macros-plugin’s include_yaml configuration.

Changes:

• Introduce SnippetVarResolverPlugin with YAML variable loading + placeholder replacement in on_page_content.
• Register the new plugin entry point and bump package version to 0.1.0a11.
• Add dedicated documentation and a new test suite for the resolver behavior.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
plugins/snippet_var_resolver/plugin.py	Implements YAML loading from macros.include_yaml and regex-based placeholder substitution on page HTML.
pyproject.toml	Registers the plugin entry point and bumps the project version.
docs/snippet-var-resolver.md	Documents the motivation, usage, and behavior/limitations of the plugin.
tests/snippet_var_resolver/test_snippet_var_resolver.py	Adds unit tests for dotted-path lookup, substitution behavior, and YAML include loading/merging.
plugins/snippet_var_resolver/__init__.py	Package marker for the new plugin module.
tests/snippet_var_resolver/__init__.py	Package marker for the new test module.

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[0xlukem]

LGTM :)