Milestone 4 Release (3.0.0)

What's Changed

• rename and modify code_of_conduct by @jessie-liang in #46
• Modify pip install command for billsplittermds by @quandothoang in #49
• add workflow changes by @quandothoang in #48
• Fix the default redirection of GitHub page to be readme.md and not contributing.md by @mayitoxix in #50
• Use Decimal for currency calculations in amount_to_transfer by @Spanorti08 in #52
• Dev - Small README typo fix by @Spanorti08 in #58
• Merge dev into main by @Spanorti08 in #59
• Add full usage demonstration for BillSplitterMDS by @quandothoang in #66
• Add reflections and its reference in website by @mayitoxix in #67

Full Changelog: 2.0.0...3.0.0