Added a migration tool!

This small tool can automatically rewrite ds_ calls in your GMS2 project(s) to use qs_, including accessors.

It can help with both permanent migration and one-off conversion to find a source of an error before fixing it in original code.

Note: for set-operator scripts (map[?key] += val), you would want to add scripts like

/// qs_map_pre(map, key)
/// @param map
/// @param key
global._qs_map_pre_map = argument0;
global._qs_map_pre_key = argument1;
return qs_map_find_value(argument0, argument1);

and

/// qs_map_post(value)
qs_map_set(global._qs_map_pre_map, global._qs_map_pre_key, argument0);

these will be included in the next update.