Add characters to the standard alphabet like ĉĝŝĥĵŭ

[Jolesh]

I am making an Esperanto translation of Stardew Valley, but Esperanto has some letters not present in the standard alphabet of Stardew Valley namely ŝ, ĝ, ĉ, ŭ, ĥ and ĵ. Therefore I get some funky simbols in my translations of the game I tried several times but didn't succeed in adding them. Can somebody help me?

Links to the mod:
Nexus mods

Github