Add pagesDir config option

Relating to https://github.com/zeit/next.js/issues/875, willing to try a PR if offered guidance.

We’re building a ecommerce store from scratch with next and are close to finishing the initial architecture. The only thing bugging us is the number of folders we ended up with. The src folder would be a major improvement in our structure and the way we thought it could be done is by adding a property called pagesDir in the next.config.js configuration.

With this new options set to something like:

{
   "pagesDir": './src/pages'
}

we could keep all the source code in src, including the pages.

• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

Added description at the top of the page

Current Behavior

Pages cannot be placed within a sub folder.

Steps to Reproduce (for bugs)

Context

Your Environment

Tech	Version
next	6.0.0
node	6.x
OS	N/A
browser	N/A
etc

[timneutkens]

Just to be clear I’m strongly against any config value for this, we’ve seen tons of misusage of config values like these (looking at distDir for example). The thing I’m willing to consider is adding src/pages support, where you choose either root level pages directory or src/pages, as apparently this covers the majority use-case of why people are asking for this feature.

[timneutkens]

We are not planning to allow changing the pages directory.

However a solution for #4406 should be explored. Let’s track that in https://github.com/zeit/next.js/issues/3027