Add fades comparison to docs (#1046)

Co-authored-by: Tzu-ping Chung <[email protected]>

docs/comparisons.md

@@ -85,3 +85,15 @@ pip-run poetry -- -m poetry --help
 
 Example interaction:
 None.
+
+## pipx vs fades
+
+[fades](https://github.com/PyAr/fades) is a tool to run **individual** Python scripts inside automatically provisioned virtualenvs with their dependencies installed.
+
+* Both [fades](https://github.com/PyAr/fades#how-to-mark-the-dependencies-to-be-installed) and [pipx run](examples.md#pipx-run-examples) allow specifying a script's dependencies in specially formatted comments, but the exact syntax differs (see also [PEP 722](https://peps.python.org/pep-0722/) which seeks to standardize such syntax).
+* Both tools automatically set up reusable virtualenvs containing the necessary dependencies.
+* Both can download Python scripts/packages to execute from remote resources.
+* fades can only run individual script files while pipx can also run packages.
+
+Example interaction:
+None.