feat(colors): add more TOML default links

For some reason, `tomlFloat` was linked to `Number`. There is a `Float`
highlight group dedicated for that.

Additionally, the `tomlDate` group was linked to `Constant`. I don't
think that's necessarily a fitting group, since a date is a literal,
and while literals _are_ constants it does not seem fitting. I gave it
the `Special` link instead, since `Special` is supposed to be used
whenever there is an "other" type in a language.

colors/highlite.vim

@@ -613,6 +613,8 @@ local highlight_groups = {
 
 	--[[ 4.3.26. TOML ]]
 	tomlComment = 'Comment',
+	tomlDate  = 'Special',
+	tomlFloat = 'Float',
 	tomlKey   = 'Label',
 	tomlTable = 'Structure',