v1.39.15

• fix: document version reset on textDocument/didSave (PR: #2695)
• Update Roslyn to 5.3.0-2.25557.5 (PR: #2696)
• Update Roslyn to 5.1.0-1.25475.3 (PR: #2692)
• Update SDKs (PR: #2652)
• Add linux-bionic-arm64 build (PR: #2653)
• Update README to explain preferred Arch build process (PR: #2684)