Consider allowing capital internal vars (`$ARGS`, `$DEPS`, etc)#586

### Description As discussed in #581, perhaps we can: 1. Have a `capital_global_vars` setting 2. When it is true, add a `declare -gn ARGS=args DEPS=deps` to enable both capital and lowercase vars Another option is to have more flexibility with this kind of settings scheme: ```yaml args_varname=ARGS deps_varname=DEPENDENCIES other_args_varname=EXTRAS ```