Automatic conversion of SPDX license list HTML into rust enum

[Terkwood]

Instead of tediously copy-pasting every license identifier from the source of truth into license.rs, we should just write a tiny utility that converts the HTML table into the rust enum.

<table class="sortable">
   <thead><tr>
   <th>Full name</th><th>Identifier</th><th>FSF Free/Libre?</th><th>OSI Approved?</th><th>Text</th>
   </tr></thead>
    
   <tbody>
   <tr>
   <td><a href="./0BSD.html" rel="rdf:_239">BSD Zero Clause License</a></td>
   <td about="./0BSD.html" typeof="spdx:License">
   <code property="spdx:licenseId">0BSD</code></td>
   <td style="text-align:center"></td>
   <td style="text-align:center">Y</td>
   <td><a href="./0BSD.html#licenseText">License Text</a></td>
   </tr>
   <tr>
   <td><a href="./AAL.html" rel="rdf:_60">Attribution Assurance License</a></td>
   <td about="./AAL.html" typeof="spdx:License">
   <code property="spdx:licenseId">AAL</code></td>
   <td style="text-align:center"></td>
   <td style="text-align:center">Y</td>
   <td><a href="./AAL.html#licenseText">License Text</a></td>
   </tr>
   <tr>
   <td><a href="./Abstyles.html" rel="rdf:_75">Abstyles License</a></td>
   <td about="./Abstyles.html" typeof="spdx:License">
   <code property="spdx:licenseId">Abstyles</code></td>
   <td style="text-align:center"></td>
   <td style="text-align:center"></td>
   <td><a href="./Abstyles.html#licenseText">License Text</a></td>
   </tr>