General purpose reformating and rewording in (a few places). This should
also make markdown linting happier.
Prefer back-ticks wherever useful and use `console` for code blocks to
be executed on terminal.
Also, update references links wherever possible (including update from
'http://' to 'https://').
Usage of `(( ... ))` over `[[ ... ]]` is preferred for arithmetic expression
since the former is less error prone.
Also, unset local variable whenever possible.
