feat: updating readmes for program/cert/creds apps (#35104)

The LMS `certificates` app `README`  has been, and the
openedx core `credentials` and `programs` READMEs  have been created.
This will clarify not only what the limited responsibilities
of each of these django apps is, but also the way they interact with
each other.

FIXES: APER-2929

openedx/core/djangoapps/credentials/README.rst

@@ -0,0 +1,19 @@
+Status: Maintenance
+
+Responsibilities
+================
+The Credentials app is responsible (along with the `programs app`_)
+for communicating with the `credentials service`_, which is
+the system of record for a learner's Program Certificates, and which (when enabled by the edX
+instance) is the system of record for accessing all of a learner's credentials.
+
+.. _credentials service: https://github.com/openedx/credentials
+
+.. _programs app: https://github.com/openedx/edx-platform/tree/master/openedx/core/djangoapps/programs
+
+See Also
+========
+
+* ``lms/djangoapps/certificates``
+* ``openedx/core/djangoapps/programs``
+

openedx/core/djangoapps/programs/README.rst

@@ -0,0 +1,21 @@
+Status: Maintenance
+
+Responsibilities
+================
+The Programs app is responsible (along with the `credentials app`_)
+for communicating with the `credentials service`_, which is
+the system of record for a learner's Program Certificates, and which (when enabled by the edX
+instance) is the system of record for accessing all of a learner's credentials.
+
+It also hosts program discussion forum and program live configuration.
+
+.. _credentials service: https://github.com/openedx/credentials
+
+.. _credentials app: https://github.com/openedx/edx-platform/tree/master/openedx/core/djangoapps/credentials
+
+See Also
+========
+
+* ``lms/djangoapps/learner_dashboard/``,  which hosts the program dashboard.
+* ``openedx/core/djangoapps/credentials``
+