Expand help text for file directory short names to detail special names

Copy/pasted (with little modification) from
https://synchro.net/docs/file_section.html#AdvancedOptions -> "Short Name:"

Some short names have specially predefined meaning and it's important to
include that detail here.

src/sbbs3/scfg/scfgxfr2.c

@@ -1632,7 +1632,57 @@ void dir_cfg(uint libnum)
 		"`Directory Short Name:`\n"
 		"\n"
 		"This is a short description of the file directory which is displayed at\n"
-		"the file transfer prompt.\n"
+		"the file transfer prompt.  Some short names have specially-defined\n"
+		"meaning:\n"
+		"\n"
+		"`Temp`\n"
+		"    Reserved for temporary archive transfers.\n"
+		"\n"
+		"`Offline`\n"
+		"    This short name specifies that this directory is to hold\n"
+		"    offline files for the selected library and is treated a bit\n"
+		"    differently than other directories.  It will not be included\n"
+		"    in new-scans and will be the default location of files that\n"
+		"    are removed or moved.  A directory with this short name should\n"
+		"    have the upload level set to 90 and the access level and flags\n"
+		"    set the same as the library.  There can only be one directory\n"
+		"    per library with this short name.\n"
+		"\n"
+		"`Sysop`\n"
+		"    This short name specifies that this directory will be the\n"
+		"    destination for files uploaded by users with the `Z` command\n"
+		"    from the transfer section.  There should only be one directory\n"
+		"    with this short name and it should belong to the most\n"
+		"    accessible library.  A directory with this short name should\n"
+		"    have the access level set to 90 and the upload level and flags\n"
+		"    set the same as the library.\n"
+		"\n"
+		"`User`\n"
+		"    This short name specifies that this directory will be the\n"
+		"    storage point for user to user transfers.  There should only be\n"
+		"    one directory with this short name and it should belong to the\n"
+		"    most accessible library.  Users can upload a file to another\n"
+		"    user or group of users with the `/U` transfer section command.\n"
+		"    Users download files sent to them with the `/D` transfer\n"
+		"    section command.  A directory with this short name should have\n"
+		"    the access level set to 90 and the upload level and flags\n"
+		"    set the same as the library or at whatever level the sysop\n"
+		"    wishes to allows users to use the user to user transfer\n"
+		"    facilities.\n"
+		"\n"
+		"`Uploads`\n"
+		"\n"
+		"    This short name specifies that this directory will be used\n"
+		"    for uploads if the user attempts to upload to a directory where\n"
+		"    he or she does not have sufficient upload access.\n"
+		"    If you wish `all` uploads to automatically go into one specific\n"
+		"    directory, set the required upload level for all `other`\n"
+		"    directories to 90 or higher (Sysop).  If you don't want users\n"
+		"    to be able to see the files in this directory or download them\n"
+		"    until they are moved by the sysop, set the required access\n"
+		"    for your 'Uploads' directory to level 90 or higher.  Creating\n"
+		"    an 'Uploads' directory also allows 'Blind' batch uploads from\n"
+		"    the users (files need not be added to the upload queue first).\n"
 		;
 	char* dir_code_help =
 		"`Directory Internal Code Suffix:`\n"