Adding the spack package manager

[vsoch]

This will add the spack package manager! I didn't know I needed to open an issue (so I have not) and I'm noob enough with ruby so I'm not sure how to run the project locally. Let me know what else you'd like me to do for the PR!

I'll be doing a PR to add the logo to Pictogram shortly!
Update: librariesio/pictogram#19

Signed-off-by: vsoch [email protected]

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