PLT-4277: Allow larger custom emojis by resizing (#4447)

Add function to resize image using resize.Thumbnail. Add function to
resize gif using previous function. Add function to convert image.Image
to image.Palleted. Add logic to identify image type and resize them if
they are larger than MaxEmojiHeight or MaxEmojiWidth. Also increase
MaxEmojiFileSize.

* fix: Add github.com/nfnt to vendor

* fix: Fix max file size and if logic in resizeEmoji

* test: Fix and add new tests for new resize feature

* fix: Fix and update translations to fit new feature

* fix: Add requested changes

webapp/i18n/en.json

@@ -73,7 +73,7 @@
   "add_emoji.header": "Add",
   "add_emoji.image": "Image",
   "add_emoji.image.button": "Select",
-  "add_emoji.image.help": "Choose the image for your emoji. The image can be a gif, png, or jpeg file with a max size of 64 KB and dimensions up to 128 by 128 pixels.",
+  "add_emoji.image.help": "Choose the image for your emoji. The image can be a gif, png, or jpeg file with a max size of 1 MB. Dimensions will automatically resize to fit 128 by 128 pixels but keeping aspect ratio.",
   "add_emoji.imageRequired": "An image is required for the emoji",
   "add_emoji.name": "Name",
   "add_emoji.name.help": "Choose a name for your emoji made of up to 64 characters consisting of lowercase letters, numbers, and the symbols '-' and '_'.",