Implement Overte Authentication and Add Test Entities

- Added documentation for Overte authentication implementation in `docs/OVERTE_AUTH.md`.
- Introduced new GLB files for cube and sphere primitives in `examples/primitives/`.
- Created a JSON file `examples/test_entities.json` containing sample entities for testing.
- Added a build and test script `scripts/build_and_test.sh` for streamlined building and verification of the project.
- Implemented a CI test runner script `scripts/ci-test.sh` to automate testing processes.
- Created a script `scripts/run_with_auth.sh` to facilitate running the Starworld client with Overte authentication.

scripts/run_with_auth.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# Run starworld with authentication
+
+echo "Overte Domain Authentication"
+echo "=============================="
+echo ""
+echo -n "Username: "
+read username
+echo "(Password no longer sent; Overte uses keypair signatures. Username is optional for now.)"
+echo ""
+export OVERTE_USERNAME="$username"
+
+echo "Connecting to Overte domain..."
+./build/starworld