[feat](trx-rs): add ft8 decoder

Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

external/ft8_lib/ft4_ft8_public/nonstd_to_c58.f90

@@ -0,0 +1,24 @@
+program nonstd_to_c58
+  
+  integer*8 n58
+  character*11 callsign
+  character*38 c
+  data c/' 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ/'/
+
+  nargs=iargc()
+  if(nargs.ne.1) then
+     print*,'Usage:    nonstd_to_c58 <callsign>'
+     print*,'Examples: nonstd_to_c58 PJ4/K1ABC'
+     print*,'          nonstd_to_c58 YW18FIFA'
+     go to 999
+  endif
+  call getarg(1,callsign)
+
+  n58=0
+  do i=1,11
+     n58=n58*38 + index(c,callsign(i:i)) - 1
+  enddo
+  write(*,1000) callsign,n58,n58
+1000 format('Callsign: ',a11/'c58 (binary):   ' b58.58/'c58 (decimal):',i20)
+  
+999 end program nonstd_to_c58