core: add command /reset to reset options to their default values

tests/unit/core/test-core-command.cpp

@@ -389,6 +389,16 @@ TEST(CoreCommand, Repeat)
     /* TODO: write tests */
 }
 
+/*
+ * Tests functions:
+ *   command_reset
+ */
+
+TEST(CoreCommand, Reset)
+{
+    /* TODO: write tests */
+}
+
 /*
  * Tests functions:
  *   command_save