[Feature] envelope

[NithyaNN3]

• added envelope function + added test cases

[aardrop]

Hey @NithyaNN3 and @deanpapas, did you all mean to have these two features together in one PR? It looks like the square feature and the envelope are both in this PR.

Best practice is 1 feature to 1 PR unless @lukas-h wants it this way. I'm comfortable reviewing as is in favor of expedience, but wanted to make sure this is intentional.

[NithyaNN3]

Hey @aardrop, please ignore this PR but all our commits will be squashed and sent in together with Dean's fork unless you prefer we change it for our next sprint.
I was trying to create a PR to merge my branch with Dean's main fork but it created one here instead