This ensures that LSP diagnostics of files which are not manually opened
by users are rendered by nvim-tree diagnostic indicators.
However when users attach an LSP to nvim-tree this will bring back
flashing as attempted to fix in #2980. Fixing this should probably done
by checking data passed via diagnostic events (DiagnosticChanged and
CocDiagnosticChanged).
Signed-off-by: des-b <66919647+des-b@users.noreply.github.com>
28eac2801b