Words ending with -tch are incorrectly pluralised

Words ending with "-tch" are pluralised to "-tchs", but they should generally be "-tches".
```
julia> using Inflector

julia> Inflector.to_plural("witch")
"witchs"

julia> Inflector.to_plural("hutch")
"hutchs"
```
Expected behaviour:
```
julia> Inflector.to_plural("witch")
"witches"
```

Start at the Inflector.to_plural entry point and reproduce the issue with the Julia examples for “witch” and “hutch.” Update the pluralization rule for words ending in “-tch,” then verify that those examples produce the expected “-tches” forms.

Written by the indexing model from the issue text.