Add word-count exercise

config.json

@@ -4,6 +4,7 @@
   "repository": "https://github.com/exercism/xracket",
   "active": false,
   "problems": [
-    "bob"
+    "bob",
+    "word-count"
   ]
 }

word-count/example.rkt

@@ -0,0 +1,8 @@
+#lang racket
+
+(define (word-count word)
+  (for/fold ([result (hash)])
+            ([word (in-list (string-split word))])
+            (hash-set result word (add1 (hash-ref result word 0)))))
+
+(provide word-count)

word-count/word-count-test.rkt

@@ -0,0 +1,38 @@
+#lang racket
+
+(require rackunit
+         rackunit/text-ui
+         "word-count.rkt")
+
+(define suite
+  (test-suite
+    "Tests for the word-count exercise"
+    (check-equal? (word-count "word")
+                  '#hash(("word" . 1))
+                  "one word")
+    (check-equal? (word-count "one of each")
+                  '#hash(("one" . 1) ("of" . 1) ("each" . 1))
+                  "one of each")
+    (check-equal? (word-count "one fish two fish red fish blue fish")
+                  '#hash(("one" . 1) ("fish" . 4) ("two" . 1) ("red" . 1) ("blue" . 1))
+                  "multiple occurrences")
+    (check-equal? (word-count "car : carpet as java : javascript!!&@$%^&")
+                  '#hash(("car" . 1) (":" . 2) ("carpet" . 1) ("as" . 1) ("java" . 1)
+                                     ("javascript!!&@$%^&" . 1))
+                  "preserves punctuation")
+    (check-equal? (word-count "testing 1 2 testing")
+                  '#hash(("testing" . 2) ("1" . 1) ("2" . 1))
+                  "include numbers")
+    (check-equal? (word-count "go Go GO")
+                  '#hash(("go" . 1) ("Go" . 1) ("GO" . 1))
+                  "mixed case")
+    (check-equal? (word-count "wait for       it")
+                  '#hash(("wait" . 1) ("for" . 1) ("it" . 1))
+                  "multiple spaces")
+    (check-equal? (word-count "rah rah ah ah ah\nroma roma ma\nga ga oh la la\nwant your bad romance")
+                  '#hash(("rah" . 2) ("ah" . 3) ("roma" . 2) ("ma" . 1) ("ga" . 2) ("oh" . 1)
+                                     ("la" . 2) ("want" . 1) ("your" . 1) ("bad" . 1)
+                                     ("romance" . 1))
+                  "newlines")))
+
+(exit (if (zero? (run-tests suite)) 0 1))