[mm-29] - Adds a confirmation button when creating a meeting on channels

[maisnamraju]

Summary

Fixes #29 It adds a warning whenever there are members in a channel and asks user if they want to create the meeting. This doesn't have support for the mobile UI yet though. Maybe it can go in a seperate PR or if there are references I could use for this I can get started right away.

Ticket Link

#29

[mattermod]

Hello @maisnamraju,

Thanks for your pull request! A Core Committer will review your pull request soon. For code contributions, you can learn more about the review process here.

Per the Mattermost Contribution Guide, we need to add you to the list of approved contributors for the Mattermost project.

Please help complete the Mattermost contribution license agreement?
Once you have signed the CLA, please comment with /check-cla and confirm that the CLA check is green.

This is a standard procedure for many open source projects.

Please let us know if you have any questions.

We are very happy to have you join our growing community! If you're not yet a member, please consider joining our Contributors community channel to meet other contributors and discuss new opportunities with the core team.