Add MCP2221A

[brentru]

Adds board definition for MCP2221A

@lorennorman Please note L9,

"installMethod": "python",

This is a new installMethod. For now, all it means is that the board won't appear on the New Board workflow and does not include assets.

Resolves: #136

[brentru]

@lorennorman The CI is erroring that the SCL/SDA should be an int, which is correct in V1 of the API:
https://github.com/adafruit/Wippersnapper_Protobuf/blob/master/proto/wippersnapper/i2c/v1/i2c.proto#L27

However, CircuitPython uses strings for naming rather than ints. Within I2CBusInitRequest.

For API V2, which'll be utilized by the MCP2221A, do you see any issues on your end with changing i2c_pin_scl and i2c_pin_sda from int32 type to string types?

[lorennorman]

lgtm!

If you want to loosen the JSON schema type check to also allow strings you can change boards/schema.json lines 151 and 152 to take an array of possible types, like:

              "SDA": { "type": [ "number", "string" ]},
              "SCL": { "type": [ "number", "string" ]}