User feedback for riotx

Hello devs / designers,

we did a test with some beta users with riotx and I wanted to give you the feedback:

* red numbers (unread messages) are indicating "urgent action required", however it is only unread messages. Suggestion from our designer: change the colour for non critical messages to non-red.
* some channels have red unread message number indicators, some have black message unread messages indicator and it is not clear to the users what means what.
* battery draining warning is appearing on Samsung S7
* Android notifications seem to be default for all messages, not mentions, which is overwhelming for all tested users
* Profile picture cannot be changed - this was the first action taken by some users and they got scared that the app is not usable at all because of this feature not working
* Colour overload in the chats: compared to other messaging systems, there are a lot of different colours in each channel, which makes the user experience confusing ("what do colours indicate?")

I know that this is again a list of issues like I reported in https://github.com/vector-im/riot-web/issues/12279 for riot-web, but I hope this input is valuable nonetheless.