fix(PageLayout): restore main landmark

[joshblack]

Follow-up to: #3675

Currently, we have teams in a couple of situations where either:

• A team makes use of a main landmark and therefore runs into the duplicate landmark violation
• A team uses the default main landmark from PageLayout.Content

When removing the main landmark, teams in the latter group are impacted. In this PR, we introduce an as prop to allow for teams in the first example to change the semantics of this component to as="div" as they already have a main defined.

Rollout

This is an incremental rollout strategy if our ideal here is to remove main as a landmark from PageLayout.Content. With this path, we could swap teams to use as="div" before removing the main support and also dropping as="div"

[changeset-bot]

🦋 Changeset detected

Latest commit: 245b067

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	100.7 KB (+0.01% 🔺)
dist/browser.umd.js	101.29 KB (+0.01% 🔺)

[siddharthkp]

Oof tough spot! But really good rollout plan!

[siddharthkp]

With this path, we could swap teams to use as="div" before removing the main support and also dropping as="div"

(not for this PR, but for after) How do you feel about this slight change:

Right now, the default element is main. If we want to change the default to div, folks that do not have duplicate main, would then need to wrap PageLayout.Content in a <main>

How do you feel about supporting the as prop on PageLayout.Content permanently, but with just 2 options: as: 'main' | 'div'.

So, changing the default from main to div would still be a breaking change, but it can be accompanied by a codemod that adds as="main" for instances that do not have as="div" already.

[joshblack]

@siddharthkp I like it, works for me!