fix(index.xml): unzip corpora so they are found by nltk.data.find

[tuky]

[tuky]

to fix https://github.com/nltk/nltk/issues/3028

[ekaf]

Unzipping corpora is not a fix, but a temporary workaround to handle occasional cases when a corpus reader does not properly handle zipped data. As it is increasingly common to use small devices with very limited storage space, it is preferable to fix the corpus reader rather than unzipping the data.