Slack API in Go Files

[!WARNING]
This release may mean a breaking change! Read below for more although for most folks this should all be fine.

👋 Hi folks,

I've tried my best to keep this version to just non-breaking changes but there are a couple of changes that might introduce breaking changes in rare circumstances.

If you're upgrading, please pay special attention to: * Add ID() to the Block interface by @samstarling in https://github.com/slack-go/slack/pull/1359

If you were using only what we provide in the library, this is a non-breaking change, but if not, it may be considered a breaking change.

Next release will likely bring a few required breaking changes (hard deprecations for example).

Thank you to everyone that contributed to this release 🥳

What's Changed

• feat: Slack AI & Assistants Compatibility by @MattDavisRV in https://github.com/slack-go/slack/pull/1331
• fix: Assistant Prompts and Status, send channel_id with request by @MattDavisRV in https://github.com/slack-go/slack/pull/1344
• fix: Don't require skin_tone for rich text emoji element by @calebmckay in https://github.com/slack-go/slack/pull/1341
• fix: ScheduleMessage not returning scheduled_message_id by @hussachai in https://github.com/slack-go/slack/pull/1153
• chore: Contributing Guide - Codification of Project Norms by @lorenzoaiello in https://github.com/slack-go/slack/pull/1340
• chore: Add parse channel context and host for shared channel by @fahmizulhasymi in https://github.com/slack-go/slack/pull/1353
• chore: Adding A Deprecation Notice for rtm.start (no-op) by @lorenzoaiello in https://github.com/slack-go/slack/pull/1351
• Additional field to the File structure by @rntk in https://github.com/slack-go/slack/pull/1370
• add enable_section option for UserGroup API by @sivchari in https://github.com/slack-go/slack/pull/1364
• Add ID() to the Block interface by @samstarling in https://github.com/slack-go/slack/pull/1359
• Add assistant app thread message subtype by @dorkauf in https://github.com/slack-go/slack/pull/1368

New Contributors

• @fahmizulhasymi made their first contribution in https://github.com/slack-go/slack/pull/1353
• @rntk made their first contribution in https://github.com/slack-go/slack/pull/1370
• @samstarling made their first contribution in https://github.com/slack-go/slack/pull/1359
• @dorkauf made their first contribution in https://github.com/slack-go/slack/pull/1368

Full Changelog: https://github.com/slack-go/slack/compare/v0.15.0...v0.16.0