When the / key is received outside a text entry field, discard it
In response to https://support.mozilla.org/questions/1091387
Retirement Announcement
No need for this userscript in Firefox 63+ (Oct. 2018) due to this handy preference:
(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.
(2) In the search box in the page, type or paste accessibility.typeaheadfind.manual and pause while the list is filtered
(3) Double-click the preference to switch the value from true to false
