Not enough types are fully exported

[ZeWaka]

see: DropdownEntry which despite technically being exported, isn't available in tgui-core/components nor does something like tgui-core/components/Dropdown exist

[jlsnow301]

really tempted to just make people use ComponentProps<typeof x> for these.
one day i'd like to see us remove the index barrel file. in that case, directly exporting the type would be ok.

[Kashargul]

After converting a few codebases fully to typescript, I think ComponentProps works more than well enough.