[MICROBA-1743]
Fixes an issue where we couldn't override the header and footer with the branded versiom within the Comms MFE because some of the dependencies of the branded components are not currently Webpack5 compliant. Adds a rule to make webpack5 less strict with imports that do not include a file extension.
This also includes a change so that the Comms MFE uses the Open edX branded colors/styles by default.
During our CI checks on PRs, we check to see if all code can be properly
transpiled into es5 to support IE11. We've since dropped support
officially for IE11, but the check is still present. A dependency of
TinyMCE is triggering an error in the is-es5 check.
Adding this webpack config will except the package from the check, to
prevent the CI from failing. Since we no longer support IE11, This check
is not needed, and ok to bypass.
