This is done by the used font, in the markup it's correct.
Looks like iosevka to me. Lovely font
EDIT: I wrongly assumed at a glance because of the shape of the $. On closer look the characters are much wider than iosevka. It's jetbrains mono
Because the characters '=>' have been used to simulate exactly the character '⇒' : to mean an arrow, not e.g. "equality then greater than".
It's not 'a' ⇒ 1, it's 'a' => 1, just write it out the correct way. Why are you trying to be fancy?