add existing documentation

doc/sample/FizzBuzz.im

@@ -0,0 +1,20 @@
+for i in 0 to:100 do
+    p = false
+
+    if i % 3 == 0 then
+        cout print:'fizz'
+        p = true
+    end
+
+    if i % 5 == 0 then
+        cout print:'buzz'
+        p = true
+    end
+
+    if !p then
+        cout print:'{i}'
+    end
+
+    cout cr
+end
+