Add timeit to measure test timings

tests/timeit.nim

@@ -0,0 +1,22 @@
+import std/monotimes, os, osproc, sequtils, strformat, strutils, times
+
+when isMainModule:
+  var params = commandLineParams()
+  params.apply(quoteShell)
+
+  let cmd = params.join(" ")
+  echo &"================\nRunning: {cmd}\n"
+
+  let
+
+    start = getMonoTime()
+    ret = execCmd(cmd)
+    endt = getMonoTime()
+
+    outf = getAppDir() / "timeit.txt"
+    outd = if fileExists(outf): readFile(outf) else: ""
+    outp = &"\nRan: {cmd}\nTime taken: {$(endt - start)}\n"
+
+  echo outp
+  writeFile(outf, outd & outp)
+  quit(ret)