Adding characters to PGGTokenizer for supporting starting Spanish punctuation signs

[offray]

In PGTokenizer>>sentenceTokenize: the line that says:

(( cur = $? or: cur = $!) or: (cur = $. and: streamPointer peek = $ ))

should be replaced by:

((#($? $! $¿ $¡) includes: cur) or: (cur = $. and: streamPointer peek = $ ))

so it can support Spanish starting punctuation signs (and not only English ones).

@olekscode @nikhilpinnaparaju: as I'm working with Polyglot, confirming bug fixes, reporting new fixes, like this one or even writing new documentation and new tutorials using Polyglot, I wonder if there is a particular contribution guidelines that I should follow for this repository or if just do a pull request and that's it.

Thanks,