Add module mcp3xxx

[koleo9am]

New implementation for all MCP3xxx ADC that are supported by gpiozero

[koleo9am]

This sensor module adds support for all MCP3xxx ADCs.

Usage:

sensor_modules:
  - name: mcp3201
    module: mcp3xxx
    spi_port: 0
    spi_device: 0
    type: mcp3008
    channel: 0
    differential: False
    max_voltage: 3.3

Supported types are: MCP3001, MCP3002, MCP3004, MCP3008, MCP3201, MCP3202, MCP3204, MCP3208, MCP3301, MCP3302, MCP3304, MCP3308

Sensor configuration is standard.

[Pro]

Ah nice! just saw that you created almost the same MR as I just did. Closed mine (#261)