added missing file

src/shash.nim

@@ -0,0 +1,17 @@
+# Simple hashing for the JS target.
+
+type
+  Hash* = int
+
+{.push checks: off.}
+proc sdbmHash(hash: Hash, c: int): Hash {.inline.} =
+  return Hash(c) + (hash shl 6) + (hash shl 16) - hash
+{.pop.}
+
+proc charCodeAt(s: cstring; i: int): int {.importcpp: "#.charCodeAt(#)".}
+
+template `&=`*(x: var Hash, c: int) = x = sdbmHash(x, c)
+template `&=`*(x: var Hash, s: cstring) =
+  for i in 0..<s.len:
+    let c = charCodeAt(s, i)
+    x = sdbmHash(x, c)