Bump postcss from 8.4.21 to 8.4.31 in /docs (#958)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.21 to
8.4.31.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/postcss/postcss/releases">postcss's
releases</a>.</em></p>
<blockquote>
<h2>8.4.31</h2>
<ul>
<li>Fixed <code>\r</code> parsing to fix CVE-2023-44270.</li>
</ul>
<h2>8.4.30</h2>
<ul>
<li>Improved source map performance (by <a
href="https://github.com/romainmenke"><code>@​romainmenke</code></a>).</li>
</ul>
<h2>8.4.29</h2>
<ul>
<li>Fixed <code>Node#source.offset</code> (by <a
href="https://github.com/idoros"><code>@​idoros</code></a>).</li>
<li>Fixed docs (by <a
href="https://github.com/coliff"><code>@​coliff</code></a>).</li>
</ul>
<h2>8.4.28</h2>
<ul>
<li>Fixed <code>Root.source.end</code> for better source map (by <a
href="https://github.com/romainmenke"><code>@​romainmenke</code></a>).</li>
<li>Fixed <code>Result.root</code> types when <code>process()</code> has
no parser.</li>
</ul>
<h2>8.4.27</h2>
<ul>
<li>Fixed <code>Container</code> clone methods types.</li>
</ul>
<h2>8.4.26</h2>
<ul>
<li>Fixed clone methods types.</li>
</ul>
<h2>8.4.25</h2>
<ul>
<li>Improve stringify performance (by <a
href="https://github.com/romainmenke"><code>@​romainmenke</code></a>).</li>
<li>Fixed docs (by <a
href="https://github.com/vikaskaliramna07"><code>@​vikaskaliramna07</code></a>).</li>
</ul>
<h2>8.4.24</h2>
<ul>
<li>Fixed <code>Plugin</code> types.</li>
</ul>
<h2>8.4.23</h2>
<ul>
<li>Fixed warnings in TypeDoc.</li>
</ul>
<h2>8.4.22</h2>
<ul>
<li>Fixed TypeScript support with <code>node16</code> (by <a
href="https://github.com/remcohaszing"><code>@​remcohaszing</code></a>).</li>
</ul>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/postcss/postcss/blob/main/CHANGELOG.md">postcss's
changelog</a>.</em></p>
<blockquote>
<h2>8.4.31</h2>
<ul>
<li>Fixed <code>\r</code> parsing to fix CVE-2023-44270.</li>
</ul>
<h2>8.4.30</h2>
<ul>
<li>Improved source map performance (by Romain Menke).</li>
</ul>
<h2>8.4.29</h2>
<ul>
<li>Fixed <code>Node#source.offset</code> (by Ido Rosenthal).</li>
<li>Fixed docs (by Christian Oliff).</li>
</ul>
<h2>8.4.28</h2>
<ul>
<li>Fixed <code>Root.source.end</code> for better source map (by Romain
Menke).</li>
<li>Fixed <code>Result.root</code> types when <code>process()</code> has
no parser.</li>
</ul>
<h2>8.4.27</h2>
<ul>
<li>Fixed <code>Container</code> clone methods types.</li>
</ul>
<h2>8.4.26</h2>
<ul>
<li>Fixed clone methods types.</li>
</ul>
<h2>8.4.25</h2>
<ul>
<li>Improve stringify performance (by Romain Menke).</li>
<li>Fixed docs (by <a
href="https://github.com/vikaskaliramna07"><code>@​vikaskaliramna07</code></a>).</li>
</ul>
<h2>8.4.24</h2>
<ul>
<li>Fixed <code>Plugin</code> types.</li>
</ul>
<h2>8.4.23</h2>
<ul>
<li>Fixed warnings in TypeDoc.</li>
</ul>
<h2>8.4.22</h2>
<ul>
<li>Fixed TypeScript support with <code>node16</code> (by Remco
Haszing).</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/postcss/postcss/commit/90208de8805dd762596c0028b8637ffbed23e371"><code>90208de</code></a>
Release 8.4.31 version</li>
<li><a
href="https://github.com/postcss/postcss/commit/58cc860b4c1707510c9cd1bc1fa30b423a9ad6c5"><code>58cc860</code></a>
Fix carrier return parsing</li>
<li><a
href="https://github.com/postcss/postcss/commit/4fff8e4cdc237619df1d73a444c0a8329701c1e2"><code>4fff8e4</code></a>
Improve pnpm test output</li>
<li><a
href="https://github.com/postcss/postcss/commit/cd43ed123274a92ebc13a1e8cccf1d65b8198f84"><code>cd43ed1</code></a>
Update dependencies</li>
<li><a
href="https://github.com/postcss/postcss/commit/caa916bdcbf66c51321574e2dde112ab13e8b306"><code>caa916b</code></a>
Update dependencies</li>
<li><a
href="https://github.com/postcss/postcss/commit/8972f76923e921a3c9655822382039b31b1c8e1a"><code>8972f76</code></a>
Typo</li>
<li><a
href="https://github.com/postcss/postcss/commit/11a5286f781d2a637f2c545c5e9cd661055acaab"><code>11a5286</code></a>
Typo</li>
<li><a
href="https://github.com/postcss/postcss/commit/45c55017776fc61f7815d1ea8e92d5291ca5d6c8"><code>45c5501</code></a>
Release 8.4.30 version</li>
<li><a
href="https://github.com/postcss/postcss/commit/bc3c341f589f9c15f1b56838a33d908374e537e0"><code>bc3c341</code></a>
Update linter</li>
<li><a
href="https://github.com/postcss/postcss/commit/b2be58a2eb788d12474ee1335f8ecdb9fa6225aa"><code>b2be58a</code></a>
Merge pull request <a
href="https://redirect.github.com/postcss/postcss/issues/1881">#1881</a>
from romainmenke/improve-sourcemap-performance--phil...</li>
<li>Additional commits viewable in <a
href="https://github.com/postcss/postcss/compare/8.4.21...8.4.31">compare
view</a></li>
</ul>
</details>
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