Fix readthedocs build by adding local pacakge install

Author: mollyheamazon

.readthedocs.yaml

@@ -18,6 +18,14 @@ formats:
 python:
   install:
     - requirements: docs/requirements.txt
+    - method: pip
+      path: ./sagemaker-core
+    - method: pip
+      path: ./sagemaker-train
+    - method: pip
+      path: ./sagemaker-serve
+    - method: pip
+      path: ./sagemaker-mlops
     - method: pip
       path: .
       extra_requirements: