Add "title" filed in ConversationsCanvasesCreateRequest

[Lexer11l]

Issue:
#1501

Parameter "title" is missing in ConversationsCanvasesCreateRequest, though it's available in API.

In my project I need to create canvases with title, therefore I suggest to expose "title" parameter in the request

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[salesforce-cla]

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