Fix parsing arrays with a name that's a prefix of an existing array

[JulianVennen]

If you have two arrays where the name of the second one is a prefix of the first, like this:

[[fruits]]
name = "banana"

[[fruit]] # prefix of existing array
name = "strawberry"

The library throws an "key duplication" error even though this is valid. If you swap the order of these items, the issue doesn't occur.
This is caused by a missing . in the str_starts_with check in TomlKeystore::addArrayTableNode.

I added that missing dot, added it to the success test and also added a test that verifies that invalid toml is still rejected by this check.

[JulianVennen]

Hey @vanodevium did you have time to look at this yet?