Fix typo in README

Julien LepillerWed Nov 03 22:40:17+0100 2021

f7f3a11

Fix typo in README

README.md

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Gitile requires Guile of course, in addition to the following Guile libraries:
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* guile-git (for accessing git repositories)
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* guile-connmark (for markdown highlighting)
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* guile-commonmark (for markdown highlighting)
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* guile-syntax-highlight (for other syntax highlighting.  Use commit
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  `51727cbb7fc05ef743aab2d7b16314ea1ed790e4`, it is more recent than the
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  latest release)