don't send default config values to ZLS

This will prevent config options set in the zls.json from being
overridden with default values by the extension.

VS Code, in their infinite wisdom, has chosen to default boolean config
options to false and string options to an empty string (""), ensuring
that null or undefined are never returned.

See zigtools/zls#2135

src/zls.ts

@@ -178,6 +178,16 @@ async function configurationMiddleware(
             // Make sure that `""` gets converted to `null` and resolve predefined values
             result[index] = configValue ? handleConfigOption(configValue) : null;
         }
+
+        const inspect = configuration.inspect(section);
+        const isDefaultValue =
+            configValue === inspect?.defaultValue &&
+            inspect?.globalValue === undefined &&
+            inspect?.workspaceValue === undefined &&
+            inspect?.workspaceFolderValue === undefined;
+        if(isDefaultValue) {
+            result[index] = null;
+        }
     }
 
     const indexOfZigPath = optionIndices["zig.path"];