docs: add landing index.md for multiproject build

docs/index.md

@@ -0,0 +1,55 @@
+# MADDENING
+
+**Modular Acausal Dataflow Differential Equation Node Network** — a pure-JAX,
+autodifferentiable framework for composing physical models from typed nodes
+connected by unit-aware edges. MADDENING is the base framework on which
+[MIME](../mime/) and the [MICROROBOTICA](../) IDE are built.
+
+```{toctree}
+:caption: User Guide
+:maxdepth: 2
+
+user_guide/installation
+user_guide/quickstart
+```
+
+```{toctree}
+:caption: Algorithm Guide
+:maxdepth: 2
+:glob:
+
+algorithm_guide/nodes/*
+algorithm_guide/coupling/*
+algorithm_guide/uq/*
+```
+
+```{toctree}
+:caption: Developer Guide
+:maxdepth: 2
+
+developer_guide/node_authoring
+developer_guide/testing_standards
+developer_guide/documentation_standards
+```
+
+```{toctree}
+:caption: Validation
+:maxdepth: 2
+:glob:
+
+validation/cou_template
+validation/framework_verification
+validation/soup_package
+validation/node_verification/*
+```
+
+```{toctree}
+:caption: Regulatory
+:maxdepth: 2
+
+regulatory/intended_use
+regulatory/iec62304_mapping
+regulatory/eu_mdr_guidelines
+regulatory/mdcg_2019_11
+regulatory/downstream_integration
+```