Update to webpack v5

[julienw]

(blocked by #3272)
We held off upgrading to webpack v5 until we had more time to look at it.

Here is some general information about changes in v5 and there is also a migration guide.

This issue in Fluent might be a problem for this upgrade: projectfluent/fluent.js#517 Update: it's been fixed.
There may be problems in other libraries too.

The first step will be to try it to see the problems we have.

Update: current problem is that we want to change our service worker implementation.

Once we migrate we can also revert the patch from #3346.

[howdyAnkit]

Interesting want to give this a try. Can I get Assigned for this?

[julienw]

hey @howdyAnkit , yes sure, please have a look! Let's discover our problems :-)

[howdyAnkit]

Thank you for Assigning @julienw

[howdyAnkit]

Made a PR for this not sure why it not got tagged.
Just mentioning here for reference: #3219

[julienw]

Thanks for your work @howdyAnkit ! Now I filed #3272 for the problem you found with your pull request #3234.