add base64 decoder/encoder

[tejxv]

Issue Id you have worked upon -

434

Briefly explain your program logic -

added add base64 decoder/encoder using base-64 library

Screenshots -

https://github.com/SarthakKeshari/calc_for_everything/assets/54097365/40f48afd-8336-4fe1-86ec-8a76b45dd800

By raising this PR I affirm that -

• [x] My code follows the guidelines of this project.
  

• [x] I have performed a self-review of my own code.
  

• [x] I have commented my code.
  

• [x] My code gives the correct output.
  

• [x] I affirm that I strictly follow contributing guidelines and code of conduct.

[SarthakKeshari]

@tejxv, As per the code I don't see this library ("base-64": "^1.0.0") being used. Kindly revert package.json of the library added is not being used.

[tejxv]

Hey, good catch! I was initially trying to use it but ended up doing it the vanilla way. It slipped from my mind while writing the PR lol, rest assured, I've reverted the package.json

Thanks!

[SarthakKeshari]

Congratulations 🎉 @tejxv on your contribution. Thanks for adding value to this repository. 😊

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[SarthakKeshari]

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