DOCS: Add front page cards for supported and external model implementations (#1012)

* Update front page of docs [makedocs]

* formating [makedocs]

* re-format [makedocs]

* clean up [makedocs]

* clarify language [makedocs]

* add oregon

Author: jpn--

docs/_static/theme_overrides.css

@@ -8,3 +8,7 @@ div.sd-card-header {
     font-weight: 800;
     var(--pst-font-family-base);
 }
+
+div.sd-card {
+    margin-bottom: 20px;
+}

docs/index.rst

@@ -33,6 +33,40 @@ the development and management of the ActivitySim is on the `project site <http:
         Start here to learn about developing ActivitySim, including creating
         model components, or changing the codebase.
 
+    .. grid-item-card::
+
+        :fa:`thumbs-up` |nbsp| |nbsp| Consortium Supported Examples
+
+        ^^^
+
+        The ActivitySim consortium actively supports two example models, each of which
+        can be used as a starting point (i.e. a "donor model") for new implementations.
+
+        - The `MTC Example <https://github.com/ActivitySim/activitysim-prototype-mtc>`__,
+          our one-zone system prototype. This example is originally based on MTC's Travel Model One (TM1),
+          but has evolved to be a slightly different model.
+        - The `SANDAG Example <https://github.com/ActivitySim/sandag-abm3-example>`__,
+          our two-zone system model. Some effort has been made to keep it aligned
+          with SANDAG's model, but it is not an exact copy of SANDAG's production model.
+
+    .. grid-item-card::
+
+        :fa:`square-arrow-up-right` |nbsp| |nbsp| Member Agency Models
+
+        ^^^
+
+        Several consortium member agencies have open-sourced their ActivitySim
+        implementations. These open models may or may not be complete calibrated
+        tools. Unless clearly marked, users should not assume that mlinked models are
+        "official" implementations used for policy analysis; public agencies often
+        publish in-progress model development to foster collaboration and transparency.
+        Contact the agencies directly with questions.
+
+        - `Puget Sound Regional Commission <https://github.com/psrc/psrc_activitysim>`__ (Seattle)
+        - `Atlanta Regional Commission <https://github.com/atlregional/arc-activitysim>`__
+        - `Metropolitan Council <https://github.com/Metropolitan-Council/metc-asim-model/tree/main/source/activitysim>`__ (Minneapolis-St. Paul)
+        - `Oregon Modeling Statewide Collaborative <https://github.com/OrMSC/SimOR>`__
+
 .. toctree::
    :hidden: