update or remove 404 links

[Roshanjossey]

(https://github.com/a11yproject/a11yproject.com/issues/1478)

Remove

• Accessibility Tester
• Blindspot: Hidden Biases of Good People
• Hex Naw
• Image-Color: Color Contrast Checker
• Munich Accessibility Meetup
• Paris Web Accessibility Meetup
• Stark newsletter

Update

• Simply Accessible articles to Level Access blog
• Karl Groves' web accessibility blog link to https://karlgroves.com/category/professional/accessibility/
• Inclusion: Diversity, The New Workplace & The Will To Change book link to https://jenniferbrownspeaks.com/jbs-book-inclusion
• Landmarks browser extension link to https://chrome.google.com/webstore/detail/landmark-navigation-via-k/ddpokpbjopmeeiiolheejjpkonlkklgp
• NoCoffee browser extension link to https://addons.mozilla.org/en-US/firefox/addon/nocoffee/
• Philly Accessibility Meetup link to https://a11yphl.com/events/
• I want to see like the colour blind chrome extension to Colorblindly chrome extension

[SaptakS]

Hi. It seems like the Hex Naw link is actually working. Apart from that all looks good.

[SaptakS]

There is a merge conflict as well, let me know if you need any help in fixing that.

[Roshanjossey]

Thank you for your review @SaptakS, I've resolved conflicts. Could you please review again?