Add Framework :: Sphinx :: Extension classifier (#28)

## Summary of changes

- Add `Framework :: Sphinx :: Extension` classifier to help people find
the extension via PyPi
- Fix keyword typo

pyproject.toml

@@ -12,13 +12,14 @@ readme = "README.md"
 authors = [{ name = "Liran Funaro", email = "[email protected]" }]
 license = { text = "MIT" }
 classifiers = [
+    "Framework :: Sphinx :: Extension",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Topic :: Software Development :: Libraries :: Python Modules"
 ]
-keywords = ["sphinx", "sphinx-extention", "markdown", "docs", "documentation", "builder"]
+keywords = ["sphinx", "sphinx-extension", "markdown", "docs", "documentation", "builder"]
 dependencies = ["sphinx>=5.1.0", "tabulate", "docutils"]
 requires-python = ">=3.7"