Updates ReadMe and add database Schema

[Vjp888]

What functionality does this accomplish?

closes #5

Description: Ensures that all endpoints are documented Adds Errors and status codes to documentation Ensures that the introduction includes my goal for this project Adds Image of the current Database Schema and connects it to the ReadMe

Current Test Suite:

Test Coverage Percentage: 100%

• [x] No Tests have been changed
• [ ] Some Tests have been changed
• [ ] All of the Tests have been changed(Please describe what in the world happened):

Checklist:

• [x] My code has no unused/commented out code
• [x] I have reviewed my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have fully tested my code
• [ ] I have partially tested my code (please explain why):

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