22 preview2 release artifacts (dotnet#1937)

* Adding 2.2 Preview 2 Release artifacts

Update Issue #

Updated links for symbols

Updated links for symbols

Update 1.0.12-download.md

Update 1.0.12-download.md

Update 1.0.12-download.md

Update 1.0.12-download.md

Merge pull request dotnet#1757 from leecow/master

Remove platforms.md and initial drop of updated releases.json

Merge pull request dotnet#1609 from dotnet/21ApiDiff

Api diff between 2.0 and 2.1