Doc: GUI->Paths panel -> helptext [update after recent additions]

[giantclambake]

For your consideration, mostly housekeeping stuff ...

-add a pointer in the ROM Path help text pertaining to the mt32-roms directory (rationale: changing this path is the easiest way to innocently 'lose' the mt32-roms dir =)

-add text pertaining to new media type paths, not to explain the obvious, but rather to explain how these tie in with GUI ops.

for ... src/osdep/gui/PanelPaths.cpp

@ line 787 ; replace with

        helptext.emplace_back("  click on the \"Rescan\" button to refresh the list of the available ROMs. Please");
        helptext.emplace_back("  note that the directory \"mt32-roms\" must exist in this location, and contain the");
        helptext.emplace_back("  required MT-32 roms if you wish to use that MIDI feature in Amiberry.");

..below the blank line at (" path if you're not using RetroArch.");

        helptext.emplace_back("- WHDboot files: This directory contains the files required by the whd-booter process");
        helptext.emplace_back("  to launch WHDLoad game archives. In normal usage you should not need to change this.");
        helptext.emplace_back(" ");
        helptext.emplace_back("- Below that are 4 additional paths, that can be used to better organize your various");
        helptext.emplace_back("  Amiga files, and streamline GUI operations when it comes to selecting the different");
        helptext.emplace_back("  types of Amiga media. The file selector buttons in Amiberry associated with each of");
        helptext.emplace_back("  the media types, will open these path locations. The defaults are shown, but these");
        helptext.emplace_back("  can be changed to better suit your requirements.");
        helptext.emplace_back(" ");

TIA