Enhance README contents

Author: sreea05

README.md

@@ -8,19 +8,35 @@ A **template** C++ library exposed to Python via [pybind11](https://github.com/p
 
 ## Table of contents
 
-- [Project structure](#project-structure)
-- [Prerequisites](#prerequisites)
-- [Quick start](#quick-start)
-- [Building](#building)
-- [Running tests](#running-tests)
-- [Test coverage](#test-coverage)
-- [Lint and format](#lint-and-format)
-- [Documentation](#documentation)
-- [Building the Python package](#building-the-python-package)
-- [CI/CD](#cicd)
-- [Usage](#usage)
-- [Recipe reference](#recipe-reference)
-- [Customizing this template](#customizing-this-template)
+- [cpp-python](#cpp-python)
+  - [Table of contents](#table-of-contents)
+  - [Project structure](#project-structure)
+  - [Prerequisites](#prerequisites)
+  - [Quick start](#quick-start)
+  - [Building](#building)
+  - [Running tests](#running-tests)
+    - [C++ tests (Google Test)](#c-tests-google-test)
+    - [Python tests (pytest)](#python-tests-pytest)
+  - [Test coverage](#test-coverage)
+    - [C++ coverage (gcovr)](#c-coverage-gcovr)
+    - [Python coverage (pytest-cov)](#python-coverage-pytest-cov)
+  - [Lint and format](#lint-and-format)
+    - [Python (ruff)](#python-ruff)
+    - [C++ (clang-format)](#c-clang-format)
+    - [Type checking (mypy)](#type-checking-mypy)
+    - [Pre-commit hook](#pre-commit-hook)
+  - [Documentation](#documentation)
+    - [C++ API docs (Doxygen + Sphinx)](#c-api-docs-doxygen--sphinx)
+    - [Python API docs (Sphinx)](#python-api-docs-sphinx)
+  - [Building the Python package](#building-the-python-package)
+  - [CI/CD](#cicd)
+  - [Usage](#usage)
+  - [Recipe reference](#recipe-reference)
+  - [Customizing this template](#customizing-this-template)
+    - [C++ library](#c-library)
+    - [C++ bindings](#c-bindings)
+    - [C++ tests](#c-tests)
+    - [Python package](#python-package)
 
 ## Project structure