Features

generate shorter output code for JSON data by using a '...' string instead of "..." (only affects output side when not minimized)
the dependencies configuration option now works for watch builds too
- It will build compilation when any of dependencies has changed
- It will wait for compiling until all of dependencies have finished
add parallelism config option on the array of configurations to limit the compilers that are running in parallel

Developer Experience

add hints (Did you mean ...) to resolve errors when
- resolving fails due to enforceExtension
- relative request is missing leading ./
when all modules of an entrypoint fail resolving and another entrypoints depend(s)On it, webpack no longer crashes with a weird error
add hint to stats how to get details about errors/warnings in child compilations
improve error message for lazyCompilation when using IE11

async entries e.g. for Workers are now implicitly flagged as "having side effects" even if they are affects by "sideEffects": false
- in future we might add a warning for this
avoid crash when using this.loadModule (loader) and the loaded module has errors
refactor libraries to inline exporting code into runtime to allow using with output.iife: false
fix invalid code when using define for local modules and arrow functions are supported
fix missing runtime requirement for system.js context
fix parsing of define function, which missed declarations before
avoid unnecessary calls to loaders when serializer are already registered
fix inner graph analysis for exports when export { x } is before pure declaration const x = /*#__PURE__*/ f()
fix hashing order of runtime chunks when there are async entries involved

improvements on experimental output.library: { type: "module" } (experiments.outputModule: true)
- it can generate export { ... } now, but that can't handle live-bindings yet