Miscellaneous feedback

Firstly and most importantly, I love this! So much that I have a bunch of feedback 😅

At least some of these should probably be separate issues but with GitHub being down at the moment I've ended up with a single dump of thoughts.

Bugs and peculiarities

• The footer shows B Toggle sidebar and Q Quit. Seeing the uppercase makes me thing I should type shit+B/shift+Q which doesn't work at all
• Up/down doesn't do anything after running uproot-browser browse uproot-Event.root. It seems like I have to click on the sidebar before I can use the keyboard to navigate
• If I click on the plot I loose the ability to nagiviate with the keyboard again
• In the browser tracebacks don't show the actual error message if I try to plot something like uproot-Event.root:event. I also think this should show a message like "Something went wrong, this probably means the branch's type isn't supported. If you think it should work the traceback below may hint at the cause of the problem."
• --iterm isn't usable with dark mode as the plot background is transparent making the black lines invisible

Features

• Add the ability to filter what is displayed in the sidebar
• Plot multiple variables on the same axis
• Apply cuts like tree->Draw("MyVar", "PT>1000")
• Set axis range/binning
• Draw expressions rather than just variables
• It would be amazing if browse could support --iterm
• Page up/down should jump a page's worth of entries when scrolling rather than just moving the view

Start with the uproot-browser browse entry point and reproduce the unchecked traceback and plotting behavior described in the issue. Separate the bundled feedback into focused tasks before investigating further. Done would require an agreed subset of the requested bugs or features to work as described, with each selected behavior verified in the browser.