CONTRIBUTING.md: Add some style guidelines
CONTRIBUTING.md: Add some style guidelines

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timfel/squeakvm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm