Publish v1.2.2 release

A excellent markdown preview extension for Visual Studio Code, Version 1.2.2.
https://marketplace.visualstudio.com/items?itemName=jhuix.markdown-preview-showdown

1. Delete condition of files.autoSave to accelerated rendering when upate text of preview page.

2. Remove extension event of onDidSaveTextDocument.

3. Accelerated rendering for plantuml using java single process.