Make headerNav hide when page is scrolled down

[brianrahadi]

Sometimes the page looks weird since the NavBar and the text can clash with each other. It would be better if the headerNav hides itself and only pops up if either view is at the top-most or the last action is scrolling up.

Example clashing:

Reference:

• https://systemshacks.com/
• https://github.com/ssss-sfu/2023-roothacks (The repo)