Fix responsive around sidebar on blog

[tnir]

Fix responsive layout broken after blog migration (#7247)

For mobile, we would see as below:

[k8s-ci-robot]

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[tnir]

Here is a screenshot of https://deploy-preview-8281--kubernetes-io-master-staging.netlify.com/blog/ on width 320px, which is not perfect (it has 460px):

[Bradamant3]

/assign @tehut
/assign @alexcontini

Sorry if the assign tags are spam, but I figure someone who's worked on the CSS and on the blog migration should take a look. It looks to me as though probably we need other fixes as well, so not sure this PR is the right direction to take. Maybe? If y'all are good with it, an /lgtm will let sig-docs approve and merge. If not, feel free to review or close as you see fit. Or if you don't have permissions, lmk. Thanks!

[k8s-ci-robot]

@Bradamant3: GitHub didn't allow me to assign the following users: tehut.

Note that only kubernetes members and repo collaborators can be assigned.

In response to this:

/assign @tehut
/assign @alexcontini

Sorry if the assign tags are spam, but I figure someone who's worked on the CSS and on the blog migration should take a look. It looks to me as though probably we need other fixes as well, so not sure this PR is the right direction to take. Maybe? If y'all are good with it, an /lgtm will let sig-docs approve and merge. If not, feel free to review or close as you see fit. Or if you don't have permissions, lmk. Thanks!

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[tnir]

/assign @chenopis

[zacharysarah]

@tnir 👋 We've migrated the site's framework to Hugo. Please re-open this PR with changes to files in their post-migration location (/content/en/blog/...) and reference this PR in the new PR's description.

[tnir]

@zacharysarah Thank you for you review. I just updated this with a newer PR.