Provide an interactive form to record the entry to the diary bot

[mrsimpson]

Motivation

Writing the daily activity in markdown is cumbersome and error-prone.

Solution

When clicking the button provided by the bot, a form shall be opened as a dialog. After completing the form, the formatted message to the bot shall be generated and sent.

Relations

• Addresses #22
• has the same limitations / boundariy conditions as #41 : When implementing this feature, it has to work on mobile as well. Thus, the feature to define a form-based-dialog needs to be provided by RC core / contributed (see https://github.com/RocketChat/Rocket.Chat/pull/12626#issuecomment-455186632)