Reorganize project. Add folder for shared code between backend/dashboard. Switch from jest to ava for tests.

backend/src/uptime.ts

@@ -0,0 +1,9 @@
+let start = 0;
+
+export function startUptimeCounter() {
+  start = Date.now();
+}
+
+export function getCurrentUptime() {
+  return Date.now() - start;
+}