Implement nodelist in the Doc tag so it may be visited

Fix History.md

Merge pull request Shopify#1905 from Shopify/catlee/invalid_utf8

Raise SyntaxError on invalid UTF8 strings in lexer/tokenizer

Version 5.7.2

Apply the same fix for `find_index` and `has`

Bump to 5.7.0 (Shopify#1894)

* Bump to 5.7.0

* Update 'History.md'

* Update 'Releasing' steps

* Update CONTRIBUTING.md

Co-authored-by: Gray Gilmore <graygilmore@gmail.com>

* Update History.md

Co-authored-by: Ian Ker-Seymer <ian.kerseymer@shopify.com>

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Co-authored-by: Gray Gilmore <graygilmore@gmail.com>
Co-authored-by: Ian Ker-Seymer <ian.kerseymer@shopify.com>

Version 5.6.4

Version 5.6.3

Version 5.6.2

Version 5.6.1