Cancel Subscription Feedback

Just tried to provide this feedback at hackmd.io while (unfortunately) canceling a subscription.

I know this repo is not for the hackmd.io service. However I think the feedback I wanted to provide is relevant to this repo. Could result in changes to codimd. Note - the feedback form component or backend may not be working right now, not sure.

### Feedback:
To HackMD, I really like this product for development projects that do not require different types of view integration (spreadsheets, website embeds, video embeds, etc). I know that this is technically possible given markdown's syntax & your rendering, but I do not feel the user experience matches that of something like Notion.

I personally do not mind this, but I know that the other non-devs on my team need something with more built-in tools for collaboration.