when loaded by luaL_loadstring, the stacktrace is very hard to read, also, there's no generic ways to format it
so, it's better to let user to customize the format rules
also, the PR export dbg.COLOR_GRAY series, then users are able to customize colorful output
when loaded by `luaL_loadstring`, the stacktrace is very hard to read, also, there's no generic ways to format it
so, it's better to let user to customize the format rules
also, the PR export `dbg.COLOR_GRAY` series, then users are able to customize colorful output