Add Bundler 2.6 to docs site, and a release blog post

[deivid-rodriguez]

What was the end-user problem that led to this PR?

The problem was that Bundler 2.6 is still not included in the documentation site, and that we should present the new stuff in Bundler 2.6.

What is your fix for the problem, implemented in this PR?

My fix is to add the new version to documentation and write a blog post about it.

[olleolleolle]

Thanks for blogging so well!

[tnir]

@deivid-rodriguez Thanks for updating, but we need to update https://bundler.io/compatibility.html (source: https://github.com/rubygems/bundler-site/blob/master/source/compatibility.html.haml)

[deivid-rodriguez]

Thanks for blogging so well!

Haha, not so sure about that... 😅, but thank you!

@deivid-rodriguez Thanks for updating, but we need to update https://bundler.io/compatibility.html (source: https://github.com/rubygems/bundler-site/blob/master/source/compatibility.html.haml)

Nice catch, let me update that now!

[deivid-rodriguez]

@tnir Done!

[deivid-rodriguez]

@tnir Could you have another look? I'd like to publish this today!

[deivid-rodriguez]

I'll update blog post date and publish this tomorrow. If @tnir doesn't get to it, we can iterate after merge if anything else is needed.

[tnir]

@deivid-rodriguez Thanks 🌮 and sorry for the delayed response! 🎉

[deivid-rodriguez]

No problem, thanks for your review!