add all modules, better gradle setup, and elixir for server

plt-build/build.gradle.kts

@@ -0,0 +1,20 @@
+plugins {
+    id("java")
+}
+
+group = "moe.rosa"
+version = "0.1.0"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation(platform("org.junit:junit-bom:5.10.0"))
+    testImplementation("org.junit.jupiter:junit-jupiter")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}