Update Webpack to at least 4.31

[eric-burel]

We have some conflicting issues for Webpack version, necessary to build Storybook:

• This needs us to update Webpack to at least 4.31: is-map: 'return' outside of function storybookjs/storybook#9154
• This locks us to at most 4.28 to support dynamic import: Parsing of import() fails in 4.29.0 (Compilation issue, related to dynamic import) webpack/webpack#8656

But maybe the second issue is now solved so we should try a Webpack update. I've locked some package versions to bypass the first issue but it has to be temporary.

[chrysillala]

HI @eric-burel , I would like to work on this issue. Thanks!

[eric-burel]

Yep feel free to work on it, but bear in mind that we are releasing Vulcan Next, an updated version of Vulcan based on Next.js. So the Meteor version is considered legacy, and mostly maintained by people that were already using it for their app.

[chrysillala]

@eric-burel please check my PR here #2731 and kindly let me know your feedback :) thanks!