feat(platform): add slack platform support (#385)

* feat(platform): add slack platform support

* docs: add slack channel setup guide

* feat: normalize slack unicode reactions

* chore(docs): remove unsupport feature

* fix(slack): harden adapter stream and identity handling

- ignore reaction and speech stream events in Slack outbound
  streams
  - normalize Slack conversation types to framework-standard values
  - route DiscoverSelf through the adapter API factory
  - add config-scoped Slack user display-name caching
  - expand adapter interface assertions and add regression coverage
  - add ChannelTypeSlack to well-known channel constants

go.mod

@@ -121,6 +121,7 @@ require (
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/kenshaw/emoji v0.4.1 // indirect
 	github.com/klauspost/compress v1.18.4 // indirect
 	github.com/labstack/gommon v0.4.2 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
@@ -157,6 +158,7 @@ require (
 	github.com/segmentio/asm v1.2.1 // indirect
 	github.com/segmentio/encoding v0.5.4 // indirect
 	github.com/sirupsen/logrus v1.9.4 // indirect
+	github.com/slack-go/slack v0.19.0 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	github.com/valyala/fasttemplate v1.2.2 // indirect