Add Regal (#327)

Regal is a linter and language server built for Rego, the language of
the Open Policy Agent project.

We've been hard at work on LSP features recently and would love to have
our project featured here.

I hope I've got the formatting all correct!

Signed-off-by: Charlie Egan <charlieegan3@users.noreply.github.com>
Co-authored-by: Charlie Egan <charlieegan3@users.noreply.github.com>

Author: charlieegan3

index.html

@@ -3025,6 +3025,32 @@ <h4>Language servers</h4>
           </td>
           <td></td>
         </tr>
+        <tr>
+          <th>Rego</th>
+          <td>
+            <a href="https://styra.com">Styra</a>
+          </td>
+          <td class="repo">
+            <a href="https://github.com/styrainc/regal">github.com/StyraInc/regal</a>
+          </td>
+          <td class="success">
+            <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
+          </td>
+          <td class="success">
+            <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
+          </td>
+          <td class="success">
+            <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
+          </td>
+          <td class="success">
+            <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
+          </td>
+          <td class="danger"></td>
+          <td class="success">
+            <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
+          </td>
+          <td>Goto Definition Request, Code Actions, Folding Range, Formatting, Inlay Hints</td>
+        </tr>
         <tr>
           <th>
             <a href="https://robotframework.org">Robot Framework</a>