Run benchmarking only on PRs

[yebai]

@shravanngoswamii In addition, we also need an option in NavBar bash script to skip a folder under gh-pages.

[shravanngoswamii]

@shravanngoswamii In addition, we also need an option in NavBar bash script to skip a folder under gh-pages.

Only for this package or all packages?

[yebai]

Only for this package or all packages?

For all packages if possible, but this should be an optional argument to the bash script if possible, so we don't need to update places where not needed.

[shravanngoswamii]

For all packages if possible, but this should be an optional argument to the bash script if possible, so we don't need to update places where not needed.

Sure, I will update the script!