add demo docs

demo/kitchen-sink/docs/forth.frt

@@ -0,0 +1,41 @@
+: HELLO  ( -- )  CR ." Hello, world!" ; 
+
+HELLO <cr>
+Hello, world!
+
+: [CHAR]   CHAR  POSTPONE LITERAL ; IMMEDIATE
+
+0 value ii        0 value jj
+0 value KeyAddr   0 value KeyLen
+create SArray   256 allot   \ state array of 256 bytes
+: KeyArray      KeyLen mod   KeyAddr ;
+
+: get_byte      + c@ ;
+: set_byte      + c! ;
+: as_byte       255 and ;
+: reset_ij      0 TO ii   0 TO jj ;
+: i_update      1 +   as_byte TO ii ;
+: j_update      ii SArray get_byte +   as_byte TO jj ;
+: swap_s_ij
+    jj SArray get_byte
+       ii SArray get_byte  jj SArray set_byte
+    ii SArray set_byte
+;
+
+: rc4_init ( KeyAddr KeyLen -- )
+    256 min TO KeyLen   TO KeyAddr
+    256 0 DO   i i SArray set_byte   LOOP
+    reset_ij
+    BEGIN
+        ii KeyArray get_byte   jj +  j_update
+        swap_s_ij
+        ii 255 < WHILE
+        ii i_update
+    REPEAT
+    reset_ij
+;
+: rc4_byte
+    ii i_update   jj j_update
+    swap_s_ij
+    ii SArray get_byte   jj SArray get_byte +   as_byte SArray get_byte  xor
+;