Accessibility Updates

[qtop1]

Your checklist for a pull request to sitespeed.io

Please review the guidelines for contributing to this repository.

• I'm making a big change or adding functionality so I've already opened an issue proposing the change to other contributors, so I got feedback on the idea before took the time to write precious code
• Check that your change/fix has corresponding unit tests (if applicable)
• Squash commits so it looks sane
• Update the documentation https://github.com/sitespeedio/sitespeed.io/tree/main/docs in another PR
• Verify that the test works by running npm test and test linting by npm run lint

Description

I have made changes to the homepages navigation bar in terms of the foreground and background colour, to make the contrast higher so it is accessible for users with visions impairments. To keep in line with the colour scheme of the site, I picked colours within the site and either darkened them to ensure contrast.

I used a colour contrast analyser to check to readability. And compared the colours that were previously on the site for the navigation bar in comparison to the ones I applied. Please see below:
Before::

After::

Also as I was checking the files, I saw on the about page section, there were 3 alt texts missing, so I added them.

[soulgalore]

Thank you @qtop1 for taking the time to do this, I'm gonna test it out tomorrow. Thanks again!