Fix and optimize image alt tags for better SEO

[RiccardoMasutti]

This will boost traffic and SEO (Search Engine Optimization) for Bisq.network.

It's extremely important to give images good alt attributes: alt text strengthens the message of website pages with search engine spiders and improves the accessibility of it.

[m52go]

@RiccardoMasutti these are good edits, but the index.html page is never actually rendered to the user, so these edits won't ever take effect.

Hence my other PR #279 to get rid of that page altogether...review appreciated :)

As for this PR, the changes should be made in the other files that are actually rendered like homepage_content.html, os_selector_options.html, etc.

I know this isn't intuitive...refactoring is needed.

[RiccardoMasutti]

@m52go ready to merge

[m52go]

NACK - see comment.

[RiccardoMasutti]

@m52go ty for review. fixed

[m52go]

Some small nits such as "Redhat" --> "Red Hat".

But bigger issues are more concerning: a number of images were changed when they shouldn't have been changed. This PR wasn't supposed to change image links at all -- please keep PRs focused on the declared changes. I assume these were inadvertent on your part, but for me as reviewer, identifying and correcting such changes is unexpected and time-consuming. I'm still not sure I caught all of them.

Please consider diffing your changes next time before submitting to verify nothing unintended has crept in...and of course, it's critical that you set up a testing environment if you haven't already (feel free to reach out if you're not familiar with what I'm talking about).

[m52go]

@RiccardoMasutti there was still a mistake. Testing in your local browser would easily help find these kinds of issues.

[m52go]

ACK