Fix hidden toolbar icons

[vtenfys]

Please read comment below and #246 before merging!

Fixes toolbar icon(s) which were not displaying correctly due to the button width being too small to fit - just 'home' for me though this might fix #238 (presumably depends on font rendering differences between browsers / OS).

• Add the fa-fw class to ensure all icons are the same fixed width
• Ensure padding: 0 is applied as this wasn't taking precedence over the default styles
  • Alternative approach would be to remove both the width and padding styles, which also leaves enough space to fit the icons, and doesn't appear (much?) different visually
• Remove unnecessary overflow: hidden

Before:

After:

[vtenfys]

It looks like the extension <style> tag is inconsistently inserted earlier or later than the JupyterLab widget library's <style> tag, which causes this bug to sometimes appear and sometimes not (padding: 0 correctly overrides the default without needing !important if it gets applied after the library styles). Maybe there's a bug with @jupyter-widgets/base causing this to happen?

[thomasaarholt]

Nice catch! I remember being surprised by the "new" style of the home button, but didn't give it much thought!

[martinRenou]

Thanks a lot! I've been willing to look at this issue since a long time, bug CSS is definitely not my cup of tea ahah.