Add title attribute to the iframe for the regular archive.org embed

[rickcurran]

This commit adds a Title attribute to the iframe for the regular Archive.org book embed to improve the Section 508 and WCAG 2.0 accessibility compliance.

The change here tackles the open issue #7370 "Shortcode Embeds: should include title attribute on iframe output to meet accessibility standards" (There are multiple files which have iframes without a title attribute which are to be updated via separate PRs).

This change adds a fixed text string which would be a translatable string within Jetpack's i8ln language strings.

It also updates the test file test-class.archiveorg.php to include the new title attribute.

Fixes #

Changes proposed in this Pull Request:

A title attribute with a fixed i8ln string is added to the iframe that is rendered within this piece of code.

Is this a new feature or does it add/remove features to an existing part of Jetpack?

This adds to an existing feature of Jetpack.

Testing instructions:

To test this please try adding an Archive.org book using the archiveorg-book shortcode. E.g.

[archiveorg id=Wonderfu1958 width=320 height=240]

With the code in place the rendered iframe should now have a title attribute.

Proposed changelog entry for your changes:

This commit adds a Title attribute to the iframe for the regular Archive.org embed to improve the Section 508 and WCAG 2.0 accessibility compliance.

[jeherve]

You seem to have started that branch from an outdated version of master, so this needs a rebase. Could you rebase after pulling all latest changes into your master branch, as explained here:
https://github.com/edx/edx-platform/wiki/How-to-Rebase-a-Pull-Request

[rickcurran]

Weird, I thought I'd pulled in all the latest changes before doing it. I'll go sort that out.

[rickcurran]

@jeherve I'm trying to rebase this using the Github desktop app, but it seems to think that it's up to date with master and so it won't let me start a rebase? I'd thought I'd updated from master before making my new branch so this would tie in with that behaviour – I've likely done something wrong though but not sure what! Any suggestions? (Sorry, I haven't rebased anything before so this is all new to me).

[jeherve]

I rebased the file for you. This should now be good to merge.

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello rickcurran! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer, review, and approve D32921-code before merging this PR. Thank you!

[rickcurran]

Thanks @jeherve, not sure what happened there! I'll double-check when I do the next one that I've pulled all updates from Master before making a branch for it.

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: October 1, 2019.
Scheduled code freeze: September 24, 2019

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