add support for python-version-file

README.md

@@ -20,6 +20,7 @@ This action sets up a Python environment for use in actions by:
 - Support for pre-release versions of Python.
 - Support for installing any version of PyPy on-flight
 - Support for built-in caching of pip and pipenv dependencies
+- Support for `.python-version` file
 
 # Usage
 
@@ -36,6 +37,17 @@ steps:
 - run: python my_script.py
 ```
 
+Read Python version from file:
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-python@v2
+  with:
+    python-version-file: '.python-version' # Read python version from a file
+    architecture: 'x64' # optional x64 or x86. Defaults to x64 if not specified
+- run: python my_script.py
+```
+
 Matrix Testing:
 ```yaml
 jobs: