add MS-SarifVSCode.sarif-viewer

[noraj]

• I have read the note above about PRs contributing or fixing extensions
• I have tried reaching out to the extension maintainers about publishing this extension to Open VSX (if not, please create an issue in the extension's repo using this template).
• This extension has an OSI-approved OSS license (we don't accept proprietary extensions in this repository)

Description

• This will add this extension (MS-SarifVSCode.sarif-viewer)
• I have opened an issue upstream but since it's MS I don't expect them to publish it on Open VSX
• It's a MIT license so OSI approved
• I have followed the steps here to build and test and have installed the extension successfully on Code OSS.

[filiptronicek]

Thank you!