feat: implement scanner

[KevinWu098]

Original (#141)

Authors: @jessieh9 @KevinWu098

What does this PR contain?

1. Implemented Scanner component as described in Generate QR Code For Volunteer ID Util + Implement Scanner Functionality #141
2. Added a "Success Button" in lieu of generating an actual QR code and handling a yet-to-be-determined url format.

How did you test these changes?

1. Go to /checkin/XX
2. Click Scan button
3. See CheckinModal

Attach images (if applicable)

Closes #141

Update (#181)

Authors: @Jaslavie @KevinWu098

Within Scanner, after scanning a QR code, it will display the scanned text data as the plain volunteer id

• Accepts a QR code with a text body following this schema:

interface QRCodeData {
  first_name: string;
  last_name: string;
  id: number;
}

• Handles errors accordingly

Refactor handleScannerSuccess to adjust the format of the volunteer object passed in

• Adds in number_in_party to volunteer object

When CheckinModal is submitted... the volunteer... should be checked-in and... the value of number_in_party updated

• Corrected backend routes: fix: correct backend endpoints for check in stand-up-to-trash-backend#67
• Corrected frontend calls and values

[KevinWu098]

@NwinNwin @Aokijiop PR is ready for re-review a la #181