Do not override existing PLUGS file

packages/server/express_server.ts

@@ -228,7 +228,12 @@ export class ExpressServer {
         );
       }
     }
-
+    try {
+      await this.space.getPageMeta("PLUGS");
+      console.log("PLUGS file already exists, won't override it.");
+      return;
+    } catch {
+      console.log("Writing fresh PLUGS file.");
       await this.space.writePage(
         "PLUGS",
         "This file lists all plugs that SilverBullet will load. Run the `Plugs: Update` command to update and reload this list of plugs.\n\n```yaml\n- " +
@@ -236,6 +241,7 @@ export class ExpressServer {
           "\n```"
       );
     }
+  }
 
   async reloadPlugs() {
     await this.space.updatePageList();