TOML case insensitivity

[bcomnes]

TOML is case sensitive, and we seem to be writing capitalized keys inconsistent with the rest of netlify.toml examples with this tool. We should fix that.

[kdabir]

netlifyctl site create creates a toml file with following data, which does not work properly

[Build]
  Publish = ""
  Functions = ""

I spent quite some time trying to deploy my site with the generated config and it didn't work. Please fix this.