To answer that you might want to see how it's done in other word games.
In Scrabble, any form of any word is accepted, as long as there is no apostrophe or dash ("arc-en-ciel" and "aujourd'hui", while counted as words in dictionaries, are not valid. Probably because there's no punctuation piece so you'd have to write "arcenciel" or "aujourdhui").
Because of this, you can add to a verb to make multiple conjugations, as long as they're all valid separately.
MANGE > MANGER > MANGERAI > MANGERAIENT
In crossword puzzles, any form of any word is also generally accepted. Dashes and apostrophes are sometimes signaled with dotted line on the side of the square between two letters.
Accents are ignored in both games. An
E piece in Scrabble can be used for e, é, è, ê, ë, and the e in œ. "œuvre" is written
OEUVRE in word games in French. This works even after the letters are placed, so
MANGÉ can cross with
Depending on your game it might differ, but I'd recommend going with Scrabble rules unless your game is so different they don't apply. French speakers will be familiar with it, and you'll probably able to find the resources you need online.
Here's one you could use. If you need a Scrabble-like list you'll need to remove words with a dash, remove diacritics and replace