Add GitLab to the list of supported providers

src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml

@@ -229,6 +229,18 @@
     </Environment>
   </Provider>
 
+  <!--
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+                                              ██ █▀▀██ ████ ████ ████ ▀▀ ██ ▄▄▀██
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+  -->
+
+  <Provider Name="GitLab" Documentation="https://docs.gitlab.com/ee/integration/openid_connect_provider.html">
+    <Environment Issuer="https://gitlab.com/" />
+  </Provider>
+
   <!--
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