Re-enable JsonDotNet dll. Set Unity projectversion to 2021 LTS (#794)

* Re-enable Newtonsoft.Json.dll

* Add Newtonsoft errors to Troubleshooting in the readme.

* Open the Unity example in the latest LTS version.

Author: timbotimbo

README.md

@@ -337,6 +337,52 @@ Thanks to [@PiotrxKolasinski](https://github.com/PiotrxKolasinski) for writing d
 
 ## Troubleshooting
 
+**Location:** Unity
+
+**Error:**
+
+```
+Multiple precompiled assemblies with the same name Newtonsoft.Json.dll included on the current platform. Only one assembly with the same name is allowed per platform. (Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll)
+
+PrecompiledAssemblyException: Multiple precompiled assemblies with the same name Newtonsoft.Json.dll included on the current platform. Only one assembly with the same name is allowed per platform.
+```
+
+**Solution:**
+Locate the listed dll file, in this case:
+`Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll`
+
+- Option 1:
+Delete the dll file or rename the file extension (e.g. `.dll.txt`) to stop it from being imported.
+- Option 2:
+Uninstall the package that conflicts in the Unity package manager (usually Version control, or Collab).
+The exact package can be found by looking for newtonsoft in `package-lock.json`
+
+---
+
+
+**Location:** Unity
+
+**Error:**
+
+```
+The type or namespace name 'Newtonsoft' could not be found (are you missing a using directive or an assembly reference?)
+The type or namespace name 'JObject' could not be found (are you missing a using directive or an assembly reference?)
+The type or namespace name 'JToken' could not be found (are you missing a using directive or an assembly reference?)
+The type or namespace name 'JToken' could not be found (are you missing a using directive or an assembly reference?)
+```
+
+**Solution:**
+
+Include the Newtonsoft JsonDotNet library.
+It is likely already included in your project with a wrong file extension:
+`Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll.txt`
+Rename the `.dll.txt` extension to `.dll` in your file explorer and open Unity again.
+
+Alternatively you can manually add [the library](https://docs.unity3d.com/Packages/com.unity.nuget.newtonsoft-json@3.1/manual/index.html) from the Unity package manager.
+
+---
+
+
 **Location:** Unity
 
 **Error:**

example/unity/DemoApp/Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll.txt renamed to example/unity/DemoApp/Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll

@@ -1,6 +1,6 @@
 {
   "dependencies": {
-    "com.unity.collab-proxy": "1.17.1",
+    "com.unity.collab-proxy": "2.0.3",
     "com.unity.ext.nunit": "1.0.6",
     "com.unity.ide.rider": "3.0.15",
     "com.unity.ide.visualstudio": "2.0.16",

example/unity/DemoApp/Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll.meta

@@ -1,12 +1,10 @@
 {
   "dependencies": {
     "com.unity.collab-proxy": {
-      "version": "1.17.1",
+      "version": "2.0.3",
       "depth": 0,
       "source": "registry",
-      "dependencies": {
-        "com.unity.services.core": "1.0.1"
-      },
+      "dependencies": {},
       "url": "https://packages.unity.com"
     },
     "com.unity.editorcoroutines": {
@@ -48,26 +46,8 @@
       "dependencies": {},
       "url": "https://packages.unity.com"
     },
-    "com.unity.nuget.newtonsoft-json": {
-      "version": "3.0.2",
-      "depth": 2,
-      "source": "registry",
-      "dependencies": {},
-      "url": "https://packages.unity.com"
-    },
-    "com.unity.services.core": {
-      "version": "1.4.2",
-      "depth": 1,
-      "source": "registry",
-      "dependencies": {
-        "com.unity.modules.unitywebrequest": "1.0.0",
-        "com.unity.nuget.newtonsoft-json": "3.0.2",
-        "com.unity.modules.androidjni": "1.0.0"
-      },
-      "url": "https://packages.unity.com"
-    },
     "com.unity.subsystemregistration": {
-      "version": "1.1.1",
+      "version": "1.1.0",
       "depth": 1,
       "source": "registry",
       "dependencies": {
@@ -151,7 +131,7 @@
       "url": "https://packages.unity.com"
     },
     "com.unity.xr.arsubsystems": {
-      "version": "4.2.3",
+      "version": "4.2.7",
       "depth": 1,
       "source": "registry",
       "dependencies": {
@@ -161,7 +141,7 @@
       "url": "https://packages.unity.com"
     },
     "com.unity.xr.legacyinputhelpers": {
-      "version": "2.1.9",
+      "version": "2.1.10",
       "depth": 1,
       "source": "registry",
       "dependencies": {

example/unity/DemoApp/Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll.txt.meta

@@ -1,2 +1,2 @@
-m_EditorVersion: 2022.1.13f1
-m_EditorVersionWithRevision: 2022.1.13f1 (22856944e6d2)
+m_EditorVersion: 2021.3.22f1
+m_EditorVersionWithRevision: 2021.3.22f1 (b6c551784ba3)