feat: add Minecraft 1.21.10 support

Add support for Minecraft 1.21.10 across all platforms:
- bukkit-helper-121-10: Spigot/Paper support module
- fabric-1.21.10: Fabric mod support module
- forge-1.21.10: Forge mod support module

Update version detection in Helper.java to use the new 1.21.10
helper for MC versions 1.21.10 and above.

Author: claude

bukkit-helper-121-10/build.gradle

@@ -0,0 +1,19 @@
+eclipse {
+    project {
+        name = "Dynmap(Spigot-1.21.10)"
+    }
+}
+
+description = 'bukkit-helper-1.21.10'
+
+sourceCompatibility = targetCompatibility = compileJava.sourceCompatibility = compileJava.targetCompatibility = JavaLanguageVersion.of(21) // Need this here so eclipse task generates correctly.
+
+dependencies {
+  implementation project(':bukkit-helper')
+  implementation project(':dynmap-api')
+  implementation project(path: ':DynmapCore', configuration: 'shadow')
+  compileOnly group: 'org.spigotmc', name: 'spigot-api', version:'1.21.10-R0.1-SNAPSHOT'
+  compileOnly ('org.spigotmc:spigot:1.21.10-R0.1-SNAPSHOT') {
+    exclude group: "com.mojang", module: "jtracy"
+  }
+}