Warn on invalid items in .toml files

[Wilfred]

Description

Currently typos errors on invalid section names in .typos.toml, but not invalid setting names.

Section name is an error:

[foo]
bar = "baz"

$ typos --dump-config -
TOML parse error at line 1, column 2
  |
1 | [foo]
  |  ^^^
unknown field `foo`, expected one of `files`, `default`, `type`

Setting is silently ignored:

[default]
bar = "baz"

Could typos warn or error in this case? This hides errors when you put a setting under [files] that should be under [default].

[epage]

Yeah, the error reporting mechanism our serialization library provides cannot apply it everywhere.

Cargo uses serde_ignored to collect and then warn about unknown fields which is likely a better approach than a hard error. For when the serialization library doesn't support that, cargo collects things into a catch-all bucket and manually collects those.