Add tasks for all the new languages

Task/Letter-frequency/ERRE/letter-frequency.erre

@@ -0,0 +1,25 @@
+PROGRAM LETTER
+
+DIM CNT[255]
+
+BEGIN
+
+      OPEN("I",1,"f:\errev30\erre.hlp")
+
+      REPEAT
+        GET(#1,A$)
+        L%=LEN(A$)
+        IF L%>0 THEN
+          FOR I%=1 TO L% DO
+            A%=ASC(MID$(A$,I%))
+            CNT[A%]+=1
+          END FOR
+        END IF
+      UNTIL EOF(1)
+      CLOSE(1)
+
+      FOR C%=$41 TO $5A DO
+        PRINT(CHR$(C%);CHR$(C%+32);": ";CNT[C%]+CNT[C%+32])
+      END FOR
+
+END PROGRAM