As explained in issue #1844 and in issue
https://github.com/webpack/webpack/issues/15007#issuecomment-996615250,
the way we used the `browser`-field was wrong.
The main reason for using the `browser`-field is the requirement of
`require('fs')` in the main-entry-file.
The workaround for this was using `require('handlebars/lib/handlebars')`,
but now it will also work via `require('handlebars')` for bundlers that
respect the `browser`-field.
The `"./runtime"`-config was removed, because it didn't have any effect.
In order to detect regressions, the webpack-integration test was
extended to test with different webpack versions.
Fixes#1174Closes#1844
Jakob Linskeseder