Move webpackManifest to below body

[KyleAMathews]

It can get quite large on big sites so blocks the initial render.

We'd need to revisit how to ensure webpack doesn't start working until this is read in.

Requested in reactjs/react.dev#179

[Daniel15]

how to ensure webpack doesn't start working until this is read in.

I'm not very experienced with Webpack, but won't everything "just work" if all the JS is at the bottom of the body, as long as this manifest is above all the other JS? Since Gatsby sites work without JS (I assume), it would make sense to defer as much of it as possible.

[KyleAMathews]

eh probably :-) I haven't thought about this stuff for 6 months so I'd need to research to remember why I moved it back to the top.

But yeah, I don't think this is a very hard fix.

[szimek]

@KyleAMathews What exactly is this webpackManifest used for? Does it list all pages? We're planning to use Gatsby and Contentful to run a blog with ~5000 pages, so it will probably get quite huge - assuming a single entry is ~60 bytes, it will be additional ~300kB on each page?

[szimek]

@KyleAMathews This issue can be closed now thanks to #3519.

[KyleAMathews]

@szimek thanks again for the PR!