fix: use TCGdex.URI to build url

[HellLord77]

previously TCGdex.URI was completely unused. this pr allows modifying this variable to point custom host.

from tcgdexsdk import TCGdex

TCGdex.URI = "http://localhost:3000/v2"  # modify host for every subsequent fetch/fecth_list calls

tcgdex = TCGdex("en")
tcgdex.URI = "http://localhost:3000/v2"  # modify only for this tcgdex object

[Aviortheking]

Thanks for the PR, I did some more work on top of it in #9 to make it more consistent with the rest of the SDKs