Add 7Zip versions "20.0.0-alpha" (#2088)

* Create 20.0.0-alpha.json

* Rename 20.0.0-alpha.json to 20.0.0-alpha.yaml

* Update 20.0.0-alpha.yaml

Support silent install

manifests/7Zip/7Zip/20.0.0-alpha.yaml

@@ -0,0 +1,20 @@
+Id: 7zip.7zip
+Name: 7Zip
+AppMoniker: 7zip
+Version: 20.0.0-alpha
+Publisher: 7zip
+Author: 7zip
+License: Copyright (C) 1999-2020 Igor Pavlov. - GNU LGPL
+LicenseUrl: https://7-zip.org/license.txt
+MinOSVersion: 10.0.0.0
+Homepage: https://www.7-zip.org/
+Description: Free and open source file archiver with a high compression ratio.
+Tags: "7zip,compression,file compression,utility,tool,zip"
+InstallerType: exe
+Installers: 
+  - Arch: x64 
+    Url: https://7-zip.org/a/7z2000-x64.exe
+    Sha256: 93b1739c237179186d4da1a6c0e821e208663915d3f1bbd7a4377d96aa6894a4
+    Switches:
+      Silent: /S
+      SilentWithProgress: /S