Add number_with_commas to NumberFormat enum

[DJafari]

for my database i have a column with number_with_commas number format

"Count": {
	"id": "%3Dk%60U",
	"name": "Count",
	"type": "number",
	"number": {
		"format": "number_with_commas"
	}
},

i getting this exception :

"number_with_commas" is not a valid backing value for enum "Notion\Databases\Properties\NumberFormat"

this PR solve this bug

[mariosimao]

Released on version 1.8.0.