docs: adjust github template and readme

[mhuynh5757]

Submission Checklist

• [x] ~The CHANGELOG.md reflects any feature, bug fixes, or known issues made in the source code~
• [x] ~New unit tests and integration tests have beed added~
• [x] ~Code coverage is more or equal to the previous coverage~
• [x] A visual inspection of the Files changed tab was made prior to submitting the pull request ensuring the style guide was followed
• [ ] CI pipeline is green
• [x] ~Included screenshot if necessary~

Description

Update template and readme.

Breakdown

• Update PR template to remind collaborators to update the readme if necessary
• Update readme

Validation

• N/A

Additional Notes

N/A

Contributing to Twilio

All third-party contributors acknowledge that any contributions they provide will be made under the same open-source license that the open-source project is provided under.

• [x] I acknowledge that all my contributions will be made under the project's license.