Add bookmarks for checking websites.

Bookmarks.md

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+- https://www.hardenize.com/
+- https://cryptcheck.fr/
+- https://www.ssllabs.com/ssltest/index.html
+- https://github.com/Brunty/awesome-checker-services
+- https://internet.nl/ Email & Internet checks
+- https://urlscan.io/
+- https://robotstoolkit.com/ && https://technicalseo.com/tools/robots-txt/
+- https://en.ryte.com/website-checker/
+- https://nibbler.insites.com/en_US
+- https://websniffer.com/
+- https://validator.w3.org/feed/ (feed validation service)
+- https://tools.pingdom.com/
+- https://www.webpagetest.org/
+- https://sitechecker.pro/
+- https://www.websitecarbon.com/
+
+## Accessibility
+- https://achecks.org/achecker
+- https://wave.webaim.org/
+- https://www.toptal.com/designers/colorfilter