Allow Linux install script to be run from anywhere

[spenserblack]

I at least don't see a reason to not do this, unless I'm missing something 🤔
Instead of requiring the user to be in the monaspace directory, this would allow them to, for example, run ./Downloads/monaspace/util/install_linux.sh.

This change could most likely be applied to install_macos.sh, too, but I didn't want to apply that since I'm not a MacOS user and am unable to do a quick test.

Love this font, BTW ❤️

---

Edit: Oof, looking at the old PRs, I see there's a lot of activity regarding installation. I hope I'm not duplicating anything.

[idan]

We removed all of the installer scripts because granular packages × different OSes means a lot of logic. Sorry! 😿

[spenserblack]

We removed all of the installer scripts because granular packages × different OSes means a lot of logic. Sorry! 😿

No problem!

But I think the install/upgrade instructions for MacOS are outdated, in that case:

monaspace/README.md

Lines 128 to 132 in 69a44ef

	There is also a script that automates the deletion of all Monaspace fonts from `~/Library/Fonts` and then copies over the latest versions. Invoke it from the root of the repo like:
	```bash
	$ bash util/install_macos.sh
	```