chore: fix main README

It was mentioning pip behaviour rather than referencing
the packagers.

Author: sgaist

README.md

@@ -16,7 +16,14 @@ The buildpack is published for consumption at
 `paketobuildpacks/python-packagers`.
 
 ## Behavior
-This buildpack participates if `requirements.txt` exists at the root the app.
+This buildpack participates if one of the following detection succeeds:
+
+- (conda)[conda/README.md] -> `environment.yml`
+- (pip)[pip/README.md] -> `requirements.txt`
+- (pipenv)[pipenv/README.md] -> `Pipfile`
+- (poetry)[poetry/README.md] -> `pyproject.toml`
+
+is present in the root folder.
 
 The buildpack will do the following:
 * At build time: