AspNetCoreServiceProviderSlackRequestListener creates its own scope w…

…hen in socket mode

Updating readme and adding EventsExample readme

Adding Description to block Option

Registering ISlackRequestContextFactory in containers

Merge branch 'master' into socketmode

Add Files and Block to SlackBot SlackMessage

- fixed: `SlackBot.CreateSlackMessage`: missing assignment of `Blocks`
- added: `SlackBot.CreateSlackMessage`: added assignment of `Files`
- added: `IMessage.Files` and `SlackMessage.Files` List

closes soxtoby issue soxtoby#77

Removing EventCallback.AuthedUsers

Marking deprecated APIs as Obsolete and updating readme

Resolves soxtoby#63

Fix bug where user blocks are not deserialised

Adding TimePicker block element