Return the mime-type of a file with the help of Ambient

> s:GetMimeType s:GetMimeType
application/x-amigados

History:
02-Mär-2025: v1.1
  fix: resolve relative paths, because RxCmd can't handle them
  new: check if the file exists

 PERMSSN    UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[Amiga]                    285     439  64.9% -lh5- c5fd Mar  2 15:52 GetMimeType/GetMimeType.readme
[Amiga]                    470     786  59.8% -lh5- ea01 Mar  2 15:51 GetMimeType/S/GetMimeType
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         2 files     755    1225  61.6%            Mar  3 00:30