fix: type definitions

Author: saecki

types/null-ls/init.tl

@@ -1,12 +1,24 @@
 local record NullLs
     record Source
         name: string
+        meta: Meta
         method: MethodKind
+        filetypes: {string}
         generator: Generator
     end
 
+    record Meta
+        url: string
+        description: string
+    end
+
     record Generator
         fn: function(Params): {Action}
+        opts: Opts
+
+        record Opts
+            runtime_condition: function(Params)
+        end
     end
 
     record Action