Add header info file for Nightbot

src/schemas/nightbot.ts

@@ -0,0 +1,21 @@
+import Joi from "joi";
+
+export const nightbotCustomHeadersSchema = Joi.object({
+	"nightbot-response-url": Joi
+		.string()
+		.uri({ scheme: `https` })
+		.optional(),
+	"nightbot-user": Joi
+		.string()
+		.optional(),
+	"nightbot-channel": Joi
+		.string()
+		.optional(),
+})
+.and(
+	"nightbot-response-url",
+	"nightbot-user",
+	"nightbot-channel",
+)
+.meta({ className: `nightbotCustomHeaders` })
+.description(`The custom headers Nightbot makes requests with`);