Simplify processLayout by removing explicit promise return

[zephraph]

This unwraps the body of processLayout from the return promise it was contained in in favor of making the function async. It's just some minor house keeping. Due to the spacing changes it's a little hard to follow what happened here.

Here's a summary:

Add async

next-mdx-enhanced/loader.js

Line 60 in 452b512

async function processLayout(options, frontMatter, content, resourcePath, scans) {

Remove Promise return

https://github.com/hashicorp/next-mdx-enhanced/pull/32/files#diff-73f82623658278cf03c2acf12426f916L63

Convert resolve to return

next-mdx-enhanced/loader.js

Line 66 in 452b512

return content

Convert reject to throw

next-mdx-enhanced/loader.js

Line 96 in 452b512

if (err) throw err

Convert resolve to return

next-mdx-enhanced/loader.js

Line 114 in 452b512

return `import layout from '${normalizeToUnixPath(layoutPath)}'

[jescalan]

Thanks so much for the contribution @zephraph! This is great - a lot easier to process the diff in split view.