Added port example for Mac Users. (#740)

LuisAbrantes · czgtest · commit e46e8c5f2354 · 2019-01-21T15:43:15.000+08:00
diff --git a/README.md b/README.md
@@ -100,7 +100,7 @@ The following settings are as per sketch settings of the Arduino extension. You
 }
 ```
 - `sketch` - The main sketch file name of Arduino.
-- `port` - Name of the serial port connected to the device. Can be set by the `Arduino: Select Serial Port` command.
+- `port` - Name of the serial port connected to the device. Can be set by the `Arduino: Select Serial Port` command. For Mac users could be "/dev/cu.wchusbserial1420".
 - `board` - Currently selected Arduino board alias. Can be set by the `Arduino: Change Board Type` command. Also, you can find the board list there.
 - `output` - Arduino build output path. If not set, Arduino will create a new temporary output folder each time, which means it cannot reuse the intermediate result of the previous build leading to long verify/upload time, so it is recommended to set the field. Arduino requires that the output path should not be the workspace itself or in a subfolder of the workspace, otherwise, it may not work correctly. By default, this option is not set.
 - `debugger` - The short name of the debugger that will be used when the board itself does not have a debugger and there is more than one debugger available. You can find the list of debuggers [here](https://github.com/Microsoft/vscode-arduino/blob/master/misc/debuggerUsbMapping.json). By default, this option is not set.

Original file line number	Diff line number	Diff line change
`@@ -100,7 +100,7 @@ The following settings are as per sketch settings of the Arduino extension. You`
`100`	`100`	`}`
`101`	`101`	```
`102`	`102`	- `sketch` - The main sketch file name of Arduino.
`103`		-- `port` - Name of the serial port connected to the device. Can be set by the `Arduino: Select Serial Port` command.
	`103`	+- `port` - Name of the serial port connected to the device. Can be set by the `Arduino: Select Serial Port` command. For Mac users could be "/dev/cu.wchusbserial1420".
`104`	`104`	- `board` - Currently selected Arduino board alias. Can be set by the `Arduino: Change Board Type` command. Also, you can find the board list there.
`105`	`105`	- `output` - Arduino build output path. If not set, Arduino will create a new temporary output folder each time, which means it cannot reuse the intermediate result of the previous build leading to long verify/upload time, so it is recommended to set the field. Arduino requires that the output path should not be the workspace itself or in a subfolder of the workspace, otherwise, it may not work correctly. By default, this option is not set.
`106`	`106`	- `debugger` - The short name of the debugger that will be used when the board itself does not have a debugger and there is more than one debugger available. You can find the list of debuggers [here](https://github.com/Microsoft/vscode-arduino/blob/master/misc/debuggerUsbMapping.json). By default, this option is not set.