feat(plugin-content-blog): add setGlobalData

[kuizuo]

When I use useGlobalData hook, I only get docusaurus-plugin-content-docs data, but I didn't see any data from docusaurus-plugin-content-blog, so I wanted to give it setGlobalData.

But I think that's all there is to it.

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[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	65
🟢 Accessibility	100
🟢 Best practices	92
🟢 SEO	100
🟢 PWA	90

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[Josh-Cena]

Sorry, we're not going to accept this, because it increases bundle size by 265 kB even for our tiny blog, which is far beyond acceptable. The doc global data is mostly needed because there are theme components like navbar doc items that need to access doc data on every page, and even then, the bundle carefully optimized and assured that only critical data is made global.

Please see #4492, #6923, and a few other related issues for discussions on how we can enable you to do this in userland (currently the only way is through plugin enhancement, as outlined in #4492). But I can assure you we are not interested in making this global data available out-of-the-box, especially since there's no sign of effort to reduce bundle size. If our own theme components/hooks don't use them, it's hard, if not impossible, to determine what's the right data to be made global.