chore: Make jecs a dependency, bump jecs to v0.3.0

+ Make jecs a wally dependency instead of a file in lib. This wasn't done earlier due to wally packages not being able to be used outside of Roblox without dynamically requiring them. Now, a script is used to download the latest source of jecsfrom Github associated with the version in the manifest.

+ Bump jecs-utils to v0.1.3 and release

.luaurc

@@ -3,6 +3,6 @@
     "aliases": {
         "jecs_utils": "lib",
         "testkit": "test/testkit",
-        "jecs": "lib/jecs"
+        "jecs": "jecs"
     }
 }