Add graphs for memory and file system

**Is your feature request related to a problem? Please describe.**
Not a problem.

**Describe the solution you'd like**
Add a graph that show the memory usage and a graph that shows the file system usage.

**Describe alternatives you've considered**
I usually use conky, [here's my config](https://github.com/Naheel-Azawy/conky-config). But I was thinking of removing the panel from my conky config, I like things to be clean. So I was thinking of something like what you did and it is what I need I guess.

**Additional context**
Awesome work btw!