Work around VSC issue with formatting on save

[MikhailArkhipov]

microsoft/vscode#41194

Plan:

• Save buffer content on formatting
• if edits were created, remember that we've formatted
• upon 'file saved' event check if edits were actually applied
• if not, then execute 'format document' command and save the file
• document workaround in release notes
• remove it when upstream issue is saved.

Addresses
#590
#124
#492

[MikhailArkhipov]

94cd778

[MikhailArkhipov]

94cd778