Add yarn troubleshooting page

docs/docs/.vitepress/sidebar.ts

@@ -89,6 +89,15 @@ export const sidebar = [
                     },
                 ],
             },
+            {
+                text: "Troubleshooting",
+                items: [
+                    {
+                        text: "Yarn",
+                        link: "/self-hosting/troubleshooting/yarn",
+                    },
+                ],
+            },
         ],
     },
     {

docs/docs/self-hosting/troubleshooting/yarn.md

@@ -0,0 +1,10 @@
+---
+title: Yarn errors
+description: Fixing yarn install errors when trying to self host Ente
+---
+
+# Yarn
+
+If your `yarn install` is failing, make sure you are using Yarn Classic
+
+* https://classic.yarnpkg.com/lang/en/docs/install