Fix loading error with webpack 5+

[jbbarth]

When trying to upgrade a Rails app from webpacker 5 to 6 (still in beta but bear with me), I got the following error when launching webpack-dev-server:

ERROR in ./node_modules/@unabridged/motion/javascript/Component.js 19:8-15
Should not import the named export 'version' (imported as 'version') from default-exporting module (only default export is available soon)

It turns out I had to upgrade to webpack 5.x which provokes this error. If I understand the webpacker
README correctly, webpack 5.x is already supposed to be supported in webpacker 5. Unclear to me if
it's the default or if people tend to stick with webpack 4.x at this point.

Imo the change looks safe, but we may want to upgrade to webpack 5 in the test application to be sure.
I tried to do so but got cryptic JS errors, and I'm unsure if you want to support both webpack 4.x and
webpack 5.x in this project. I'm ready to try shaving this yak but I'll happily take your opinion
before doing so ;-)

Thanks!

[jbbarth]

Fwiw the build is passing except for Ruby 3.0.0 where we're hitting something like mimemagicrb/mimemagic#162

[jbbarth]

Closing this as I won't be able to move forward and I lost interest in making it work (switched job + they're removing Motion at my $OLD_JOB). Feel free to take my code if it helps.