Allow users to optionally override templates (#1319)

* Create overrides directory & readme.partial.yaml.j2

* Add bootstrap/overrides to makejinja.toml

makejinja.toml

@@ -1,5 +1,5 @@
 [makejinja]
-inputs = ["./bootstrap/templates"]
+inputs = ["./bootstrap/templates","./bootstrap/overrides"]
 output = "./"
 exclude_patterns = [".mjfilter.py", "*.partial.yaml.j2"]
 data = ["./config.yaml"]