Add recommendation to pca9685 (#2049)

docs/components/board/pca9685.md

@@ -81,12 +81,12 @@ The following attributes are available for `pca9685` boards:
 | ---- | ---- | --------- | ----------- |
 | `board_name` | string | Optional | The `name` of the board with GPIO pins your `pca9685` is [connected to](https://learn.adafruit.com/16-channel-pwm-servo-driver/hooking-it-up). |
 | `i2c_name` | string | Optional | The `name` of the `i2c` your `pca9685` is connected to, as configured in your main board's section of the config file. |
-| `i2c_bus` | string | Optional | The index of the board with GPIO pins your `pca9685` is connected to. Often a number. <br> Example: `”1”` |
+| `i2c_bus` | string | Optional (recommended) | The index of the board with GPIO pins your `pca9685` is connected to. Often a number. <br> Example: `”1”` |
 | `i2c_address` | int | Optional | The PCA9685's unique [I<sup>2</sup>C address](https://learn.adafruit.com/i2c-addresses/overview). |
 
 {{% alert title="Important" color="note" %}}
 
-Your PCA9685's config needs to include either just `i2c_bus`, or both `board_name` and `i2c_name`.
+Your PCA9685's config needs to include either just `i2c_bus` (recommended), or both `board_name` and `i2c_name`.
 Using `board_name` and `i2c_name` requires you to explicitly configure I<sup>2</sup>Cs on your main board, whereas using `i2c_bus` does not.
 
 {{% /alert %}}