feat(std): add string splitter

lib/std.fnl

@@ -20,5 +20,13 @@
   (or (= nil s)
       (= "" s)))
 
+(fn std.s-split [s sep]
+  (var t {})
+  (let [sep (or sep "%s")
+        re (.. "([^" sep "]+)")]
+    (each [str (string.gmatch s re)]
+      (table.insert t str))
+    t))
+
 std
 ;;; std.fnl ends here