Fixes Installation commands in README.md

[nikilpatel94]

What does this PR do?

Fixes pip installation commands.
I added quotes in pip installation commands to fix them for someone unfamiliar or less familiar try installing.

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• This PR fixes a typo or improves the docs (if yes, ignore all other checks!).
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[MaartenGr]

I work way too much on windows... If I'm not mistaken, these additional quotes are needed for Linux-based systems right?