docs: link to PyRuntimeInfo and mention it has more than example shows (#3170)

Have the example that gets the python version also link to the provider.
Also mention
that more than just the version is available.

docs/howto/get-python-version.md

diff --git a/docs/howto/get-python-version.md b/docs/howto/get-python-version.md
index 92af433..8ff9cff 100644
--- a/docs/howto/get-python-version.md
+++ b/docs/howto/get-python-version.md
@@ -35,6 +35,10 @@
 )
 ```
 
+The `info` variable above is a {obj}`PyRuntimeInfo` object, which contains
+information about the Python runtime. It contains more than just the version;
+see the {obj}`PyRuntimeInfo` docs for its API documentation.
+
 ## Using the rule
 
 In your `BUILD.bazel` file, you can use the rule like this: