docs: Add module support matrix.

index.rst

@@ -35,7 +35,7 @@ through the `Adafruit Learning System <https://learn.adafruit.com/>`_. These
 docs are low-level API docs and may link out to separate getting started guides.
 
 .. toctree::
-    :maxdepth: 2
+    :maxdepth: 3
 
     shared-bindings/index.rst
     docs/drivers.rst

shared-bindings/index.rst

@@ -3,8 +3,23 @@ Core Modules
 
 These core modules are intended on being consistent across ports. Currently
 they are only implemented in the SAMD21 and ESP8266 ports. A module may not exist
-in a port if no underlying hardware support is present. For example, a
-microcontroller without analog features will not have `analogio`.
+in a port if no underlying hardware support is present or if flash space is
+limited. For example, a microcontroller without analog features will not have
+`analogio`.
+
+Support Matrix
+---------------
+
+===============  ==========  =========  ===========  =======  =======  ===========  =================  ================  =========  ========  =========  =======  =========
+Port             `analogio`  `audioio`  `bitbangio`  `board`  `busio`  `digitalio`  `microcontroller`  `neopixel_write`  `pulseio`  `time`    `touchio`  `uheap`  `usb_hid`
+===============  ==========  =========  ===========  =======  =======  ===========  =================  ================  =========  ========  =========  =======  =========
+SAMD21           **Yes**     No         No           **Yes**  **Yes**  **Yes**      **Yes**            **Yes**           No         **Yes**   **Yes**    Debug    **Yes**
+SAMD21 Express   **Yes**     **Yes**    **Yes**      **Yes**  **Yes**  **Yes**      **Yes**            **Yes**           **Yes**    **Yes**   **Yes**    Debug    **Yes**
+ESP8266          **Yes**     No         **Yes**      **Yes**  **Yes**  **Yes**      **Yes**            **Yes**           No         **Yes**   No         Debug    No
+===============  ==========  =========  ===========  =======  =======  ===========  =================  ================  =========  ========  =========  =======  =========
+
+Modules
+---------
 
 .. toctree::
     :glob: