We're not really using much es6 features, so we might as well make this a normal function so that people with browsers that are old due to not being able to update them (such as apple devices not getting updates the os after end of life). Also replaces the `const` with a `var` since it doesn't really matter if it's modified or not and that is an es6 feature was well.
This might fix https://github.com/hack-chat/main/issues/33 or at least the issues 'CheekyChops' having. I didn't test this code, but it's such a simple change.
Solved the most annoying problem for the mobile clients, the sidebar scroll. Yeah, we've experienced this situation when we couldn't invite someone who's at the last end of the sidebar with our mobile browser cause sidebar spills out of the screen when there's a lot of users connected. But, now this is solved by fixing the height of sidebar container to 90% when shown and to 0% when hidden. Ah! I was really grieving to get rid of this shit.
