Bundle Gson on 1.11.2 and below (fixes #421)

Decided to go with 1.11.2 because the Gson from that version is the first to not
have the JsonAdapter annotiation, which we want for fixing #520.

build.gradle

@@ -228,7 +228,7 @@ def shadeExclusions = {
     // Cannot just add these to the shade configuration because they'd be inherited by the compile configuration then
     exclude group: 'com.google.guava', module: 'guava-jdk5'
     exclude group: 'com.google.guava', module: 'guava' // provided by MC
-    exclude group: 'com.google.code.gson', module: 'gson' // provided by MC
+    exclude group: 'com.google.code.gson', module: 'gson' // provided by MC (or manually bundled for 1.11.2 and below)
 }
 
 dependencies {
@@ -312,6 +312,11 @@ dependencies {
         }
     }
 
+    if (mcVersion < 11200) {
+        // The version which MC ships is too old, we'll need to ship our own
+        shadow 'com.google.code.gson:gson:2.8.7'
+    }
+
     shadow 'com.github.javagl.JglTF:jgltf-model:3af6de4'
 
     if (FABRIC) {