add hrtime utils

server/src/core/hrtime-core.ts

@@ -0,0 +1,7 @@
+/**
+ * Takes a process.hrtime.bigint(), and returns the miliseconds elapsed since it.
+ * This function will not work if more than 100(ish) days have passed since the first reference.
+ */
+export function GetMilisecondsSince(ref: bigint) {
+    return Number(process.hrtime.bigint() - ref) / 1e6;
+}