[unity] Added a second package.json for timeline UPM package for use with spine-unity via unitypackage instead of UPM dependencies. See #1676.

spine-unity/Modules/com.esotericsoftware.spine.timeline/package-no-spine-unity-dependency.json

@@ -0,0 +1,19 @@
+{
+	"name": "com.esotericsoftware.spine.timeline",
+	"displayName": "Spine Timeline Extensions",
+	"description": "This plugin provides integration of spine-unity for the Unity Timeline.\n\nPrerequisites:\nIt requires a working installation of the spine-unity runtime (via the spine-unity unitypackage), version 4.0.\n(See http://esotericsoftware.com/git/spine-runtimes/spine-unity)",
+	"version": "4.0.5",
+	"unity": "2018.3",
+	"author": {
+		"name": "Esoteric Software",
+		"email": "[email protected]",
+		"url": "http://esotericsoftware.com/"
+	},
+	"dependencies": {
+		"com.unity.timeline": "1.2.10"
+	},
+	"keywords": [
+		"spine",
+		"timeline"
+	]
+}

spine-unity/Modules/com.esotericsoftware.spine.timeline/package-no-spine-unity-dependency.json.meta

@@ -0,0 +1,7 @@
+fileFormatVersion: 2
+guid: 7d45acd6a5447f84db6c00a864838a10
+TextScriptImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

spine-unity/Modules/com.esotericsoftware.spine.timeline/package.json

@@ -1,7 +1,7 @@
 {
 	"name": "com.esotericsoftware.spine.timeline",
 	"displayName": "Spine Timeline Extensions",
-	"description": "This plugin provides integration of spine-unity for the Unity Timeline.\n\nPrerequisites:\nIt requires a working installation of the spine-unity runtime, version 4.0.\n(See http://esotericsoftware.com/git/spine-runtimes/spine-unity)",
+	"description": "This plugin provides integration of spine-unity for the Unity Timeline.\n\nPrerequisites:\nIt requires a working installation of the spine-unity and spine-csharp runtimes as UPM packages (not as spine-unity unitypackage), version 4.0.\n(See http://esotericsoftware.com/git/spine-runtimes/spine-unity)",
 	"version": "4.0.5",
 	"unity": "2018.3",
 	"author": {