Add Internal Links To Boards In The Support Matrix

[sommersoft]

Implements #2923. Allows the following: https://circuitpython.readthedocs.io/en/latest/shared-bindings/support_matrix.html#<id>

@askpatrickw was correct, rST's csv-table parsing just wouldn't allow the reference to be generated. I switched it to use a list-table, using an example in the docutils reference of applying internal hyperlink targets.

The only tricky part is utilizing the resulting hyperlink target. docutils normalizes the identifiers to conform to this regex: [a-z](-?[a-z0-9]+)*. This may prove difficult to replicate in certain instances. Programmatically, something like re.sub(r"\W+", "-") should suffice for the special characters; the rest is just lowercase and stripping non-alpha leading characters. Manually, its just a matter of looking at the HTML source on RTD I guess.

Here is an example of the resulting HTML (truncated elements, for easier reading):

<tbody id="commander">
    <tr class="row-even">
        <td><p>8086 Commander</p></td>
    </tr>
    <tr class="row-odd" id="adafruit-circuit-playground-bluefruit">
        <td><p>Adafruit Circuit Playground Bluefruit</p></td>
    </tr>
    <tr class="row-odd" id="j-j-studios-datum-light">
        <td><p>J&amp;J Studios datum-Light</p></td>
    </tr>
    <tr class="row-even" id="ndgarage-n-bit6-feathersnow-v2">
        <td><p>ndGarage[n°] Bit6: FeatherSnow-v2</p></td>
    </tr>
</tbody>

[tannewt]

Looks great! Thank you!