Website: add instructions for VSCodium

Author: strager

website/public/install/index.ejs.html

@@ -418,6 +418,55 @@ <h2>Install quick-lint-js</h2>
               <td><span aria-label="not installed"></span></td>
             </tr>
 
+            <tr>
+              <th>
+                <a href="#open-vsx">
+                  <img
+                    class="install-logo"
+                    src="../open-vsx.svg"
+                    alt=""
+                    aria-labeled-by="install-method-open-vsx"
+                  />&nbsp;<span id="install-method-open-vsx"
+                    >Open&nbsp;VSX</span
+                  ></a
+                >
+              </th>
+
+              <td class="os">
+                <img
+                  class="os-logo"
+                  src="../linux.svg"
+                  alt="GNU/Linux"
+                  title="GNU/Linux"
+                />
+              </td>
+              <td class="os">
+                <img
+                  class="os-logo"
+                  src="../macos.svg"
+                  alt="macOS"
+                  title="macOS"
+                />
+              </td>
+              <td class="os">
+                <img
+                  class="os-logo"
+                  src="../windows.svg"
+                  alt="Windows"
+                  title="Windows"
+                />
+              </td>
+
+              <td><span aria-label="not installed"></span></td>
+              <td><span aria-label="not installed"></span></td>
+              <td class="good">
+                <a href="#open-vsx"
+                  ><span aria-label="installed">✅</span></a
+                >
+              </td>
+              <td><span aria-label="not installed"></span></td>
+            </tr>
+
             <tr>
               <th><a href="#manual">Manual (pre-built)</a></th>
 
@@ -1002,6 +1051,52 @@ <h2>
         </p>
       </article>
 
+      <article id="open-vsx">
+        <h2>
+          <img class="install-logo" src="../open-vsx.svg" alt="" />&nbsp;Open VSX
+        </h2>
+        <p>
+          Supported operating systems:
+          <img
+            class="os-logo"
+            src="../linux.svg"
+            alt="GNU/Linux"
+            title="GNU/Linux"
+          />
+          <img class="os-logo" src="../macos.svg" alt="macOS" title="macOS" />
+          <img
+            class="os-logo"
+            src="../windows.svg"
+            alt="Windows"
+            title="Windows"
+          />
+        </p>
+
+        <p>
+          quick-lint-js has a VSCodium extension on the Open VSX registry.
+        </p>
+        <p>
+          Open VSCodium, open the Extensions panel, and
+          search for <kbd>quick-lint-js</kbd>.
+        </p>
+        <p>Alternatively, install the extension manually:</p>
+        <ol>
+          <li>
+          Visit the
+          <a
+            href="https://open-vsx.org/extension/quick-lint/quick-lint-js"
+            >quick-lint-js extension</a
+          >
+          page.
+          <li>Click the <em>Download</em> button.
+            <li>Open VSCodium.
+              <li>Open the Extensions panel.
+                <li>Click the "..." to open a menu.
+                  <li>Select <em>Install from VSIX...</em>.
+                    <li>Choose the <code>quick-lint.quick-lint-js-0.2.0.vsix</code> file you downloaded.
+        </ol>
+      </article>
+
       <article id="manual">
         <h2>Manual (pre-built)</h2>
         <p>