Feat discount calculator

[lalitkumawat1m]

Please describe the changes this PR makes and why it should be merged:
Added Discount Calculator

Closes #761

Status

• Code changes have been tested against prettier, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• This PR changes the codebase
  • This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
  • This PR changes the internal workings with no modifications to the external API (bug fixes, performance improvements)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
million-kitchen-sink	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 24, 2023 6:21am
sink	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 24, 2023 6:21am

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Pull Request Test Coverage Report for Build 6623107561

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 25.706%

---

Totals
Change from base Build 6580687542:	0.0%
Covered Lines:	1257
Relevant Lines:	5082

---

💛 - Coveralls

[tobySolutions]

LGTM, good job @lalitkumawat1m! Thanks for this.