LanguageServer: Handle late completion requests
LanguageServer: Handle late completion requests

Currently, Psalm Language Server is only able to handle completion
requests where the gap between a recent known type and the current
cursor position is exactly '->' or '::'. However, VS code often doesn't
send a completion request until an additional, third character has
been typed. This change allows Psalm to successfully serve
completion requests where an additional character has been typed.
vimeo/psalm,vimeo/psalm