Reconsider the laptop size cutoff

**What Happened?**
See conversation here:
https://github.com/rosariopfernandes/fireXtensions/commit/51ef0256ec62ec484197818fc58cb4357ae9a0c3#commitcomment-30765578

Our cutoff is currently 1400px but there are many laptops out there with the 1368px resolution.

**What Did You Expect to Happen**
Expected @rosariopfernandes to be able to see the sidebar!

**Screenshot (If Applicable)**
N/A

Follow the linked commit conversation first, then locate where the 1400px laptop-size cutoff is defined in the site. Verify the sidebar at a 1368px resolution; the work is done when the expected user can see it at that width.

Written by the indexing model from the issue text.