release: Add relase notes for 0.20.6
release: Add relase notes for 0.20.6

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mdhender/hugo,gohugoio/hugo,digitalcraftsman/hugo,fedelibre/hugo,fedelibre/hugo,fedelibre/hugo,gohugoio/hugo,mitchchn/hugo,mdhender/hugo,anthonyfok/hugo,anthonyfok/hugo,mdhender/hugo,mdhender/hugo,fedelibre/hugo,anthonyfok/hugo,mitchchn/hugo,gohugoio/hugo,digitalcraftsman/hugo