LSIF: warn on unknown type of item edge
Created by: chrismwendt
Prior to this change, lsif-server would throw an error when it encountered any item edge that it didn't recognize. Some indexers such as https://github.com/microsoft/lsif-java emit textDocument/typeDefinition
, which lsif-server currently doesn't support.
After this change, lsif-server will log that it didn't recognize the edge and continue processing.