I cannot figure out how to react with a :one: Emoji with DiscordJs.
Usually placing an escape \ infront of the Emoji would give you the id of the Emoji, but with \
happens
Reacting with :one: or one or the discord link doesn't work either.
(https://ptb.discordapp.com/assets/d10eead5823437c08b5287cf93bd5223.svg => 10eead5823437c08b5287cf93bd5223)
When using the symbol that @Nathn suggested, it still throws an error:

My Solution
The solution that I used was to pick "E0.6 keycap 1" from an Emoji Picker instead of "keycap 1". I recommend doing it the way @a2br suggested with creating your own emote - that way it will stay consistent across devices.
Also if you are going to put those emojis into fixed width text containers you wont need to worry about the "keycap 1" actually being 3 characters (1 + glueChar + keyCap) and rendering it as 3 characters on some devices and other devices rendering it as 1.5 width for whatever reason.