v7.7.0

Support Redelivery object for narrowcast messages #242 (@hinoguma )
Messaging API - October 2020 update - Add API for set webhook endpointURL #233 #241 (@hinoguma )
Messaging API - October 2020 update - Add API TestWebhook #233 #239 (@kkdai )
Messaging API - October 2020 update - Add API for webhook-info#233 #238 (@Thanakorn-ki )
Support message api span component in flex message #236 #234 (@wei840222 )
Messaging API - October 2020 update - Add API for get-bot-info #233 #232 (@hinoguma )