Issue title: [REQUEST] Vim keys already included?
 Issue body: I know you already added hjkl navigation to bpytop. Is it missing or am i just too stupid to find out how to configure? 

As an idea you may be able to get away with less requests like these if users could add their keybindings to the config file. Not sure how much time would go into implementing that but just a suggestion.

Have to say that i really like this version. As much as i love python this kind of thing is better written in a lower level language.
 Comments: 
 Comment 0: @jweckman 
I can't really say that I see much point in having "vim keys" in a program where you're not going to be switching between typing text and moving around especially often.

I could possibly add the keybinds for `h j k l` in upper-case, that way you can toggle them with caps-lock. But I won't remove the already set default keybindings to accommodate a very small minority of users. You would also still have to use the arrow keys to move the cursor when editing text fields.

Adding support for user customizable keybinds is no small task and isn't gonna be a high priority request right smithcynthia@example.org.
 Comment 1: Thanks for the reply. I was mainly wondering about the `h j k l` support :)

The reason why many of us are so annoying related to this detail is that it has become a core component of how we use our computers. It's not simply vim, its basically everything. Bash, zsh, tmux, less, psql, and even web browsers support the home row based navigation standard, which allows us to almost completely not use the arrow keys or the mouse for the most part. Introducing one of the core applications (yours is one of them) with arrow keys breaks the flow so badly that the slowness of bpytop becomes a significantly smaller issue.

What i'm saying is that perhaps some of your biggest fans that are really into performance optimization are now missing out on this rewrite that you spent so much time on, with no clear reason since the support was already there in the earlier version.

Personally, i would recommend against caps-lock based support, since many keyboard driven users remap their escape key to caps-lock since it is used a lot more often.

Again, thank you so much for your work. I will be fine using bpytop but i wanted you to know that this feature would mean a lot to a lot of people and that it is significant enough that maybe someone who knows C would be happy to add full keyboard customization for you. I'm more of a Python/Rust guy so i could not help you at the smithcynthia@example.org.


 Comment 2: @jweckman @itaranto 
A toggle in the options for enabling Vim keys added in v1.0.15
 Comment 3: @aristocratos Holy cow that was fast. I only realized that you added it now because Brodie Robertson covered your application on youtube. Instantly had to install on my daily driver and reconfigure all my personal ansible scripts. Thanks!
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