Update the Unleash docs navbar according to the new spec:
Changing "estimated time burden" to "estimated time" (or "estimated
reading time"), is just a matter of changing the text in the files.
There's nothing special making it say burden other than plain text. That
can be done in a follow-up PR.
The new nav bar includes the Unleash academy and certification dropdowns
as well as the docs and quickstart items. On smaller screen sizes
(between 997 and 1150 px), we hide the word "Unleash" from "Unleash
academy" and "Unleash certification".
The narrowest nav bar:
When Unleash pops back in:
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Co-authored-by: markunl <mark@getunleash.io>
