Packaging Update

# Added
- Added LICENCE.
- Added build workflow.
- Added release workflow.
- Added PackageTools.

# Changed
- Update Unity from 2020.3.1f1 to 2020.8.1f1.

Assets/PackageTools.meta

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Assets/PackageTools/Editor.meta

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Assets/PackageTools/Editor/UnityPackageExporter.cs

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+using System.IO;
+using System.Linq;
+using UnityEngine;
+using UnityEditor;
+
+namespace MackySoft.PackageTools.Editor {
+
+	public static class UnityPackageExporter {
+
+		// The name of the unitypackage to output.
+		const string k_PackageName = "SerializeReference-Extensions";
+
+		// The path to the package under the `Assets/` folder.
+		const string k_PackagePath = "MackySoft";
+
+		// Path to export to.
+		const string k_ExportPath = "Build";
+
+		const string k_SearchPattern = "*";
+		const string k_PackageToolsFolderName = "PackageTools";
+		const string k_ResourcesFolderName = "Resources";
+
+		[MenuItem("Tools/SerializeReference Extensions/Export Package")]
+		public static void Export () {
+			ExportPackage($"{k_ExportPath}/{k_PackageName}.unitypackage");
+		}
+
+		
+		public static string ExportPackage (string exportPath) {
+			// Ensure export path.
+			var dir = new FileInfo(exportPath).Directory;
+			if (dir != null && !dir.Exists) {
+				dir.Create();
+			}
+
+			// Export
+			AssetDatabase.ExportPackage(
+				GetAssetPaths(),
+				exportPath,
+				ExportPackageOptions.Default
+			);
+
+			return Path.GetFullPath(exportPath);
+		}
+
+		public static string[] GetAssetPaths () {
+			var path = Path.Combine(Application.dataPath,k_PackagePath);
+			var assets = Directory.EnumerateFiles(path,k_SearchPattern,SearchOption.AllDirectories)
+				.Where(x => !x.Contains(k_PackageToolsFolderName) && !x.Contains(k_ResourcesFolderName))
+				.Select(x => "Assets" + x.Replace(Application.dataPath,"").Replace(@"\","/"))
+				.ToArray();
+			return assets;
+		}
+
+	}
+}

Assets/PackageTools/Editor/UnityPackageExporter.cs.meta

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