Add ModConfig.Save

[Destructor-Ben]

What is the new feature?

Moves saving logic to a public method in ModConfig.
Moved from the bloated config ui rework pr - expect config.open to come soon.

Why should this be part of tModLoader?

Reflection is needed if configs are changed outside of the config menu, e,g, repositioning adrenaline and rage metres in calamity.

Are there alternative designs?

• Having the method in ConfigManager
• Not changing the nesting, even though it was horribly intended it may have been more intuitive

Sample usage for the new feature

ModContent.GetInstance<MyConfig>().Save();

ExampleMod updates

Could add an example, I didn't though.