feat: add etag to image function

Author: ascorbic

src/lib/templates/imageFunction.js

@@ -3,6 +3,7 @@ const sharp = require('sharp')
 const fetch = require('node-fetch')
 const imageType = require('image-type')
 const isSvg = require('is-svg')
+const etag = require('etag')
 
 // 6MB is hard max Lambda response size
 const MAX_RESPONSE_SIZE = 6291456
@@ -116,6 +117,7 @@ const handler = async (event) => {
     statusCode: 200,
     headers: {
       'Content-Type': `image/${info.format}`,
+      etag: etag(imageBuffer),
     },
     body: imageBuffer.toString('base64'),
     isBase64Encoded: true,