any text can be included in the reaction together with the custom emoji but client devs would need to add support for that. usually reactions are +, -, a unicode emoji or a custom emoji and people will use those most of the time so not sure if any dev will implement what you want although the protocol allows it. i'm not currently involved in nostr client development, sorry I can't help you :nostopus_crying:
Discussion
DEAR nostr:npub1qny3tkh0acurzla8x3zy4nhrjz5zd8l9sy9jys09umwng00manysew95gx PLEASE HELP ME TO SPREAD MY IDEA. CUSTOM EMOJIS ACT LIKE LINKS TO REACTIONS ITS THE SAME WAY WHEN A USER ZAPS WITH A LINK. 👻 IMAGINE THE OUTCOME N HOW ADDICTIVE THAT COULD BE FOR BOTH SIDES!