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

.zed/settings.json

@@ -21,7 +21,7 @@
             "mode": "relativeToFile",
             "fileAliases": {
               "@jecs_utils": "lib",
-              "@jecs": "lib/jecs",
+              "@jecs": "Packages/jecs",
               "@testkit": "test/testkit"
             },
             "directoryAliases": {