build: update bootstrap requirement to 4.1.0 in /packages/stryker-html-reporter (#688)
build: update bootstrap requirement to 4.1.0 in /packages/stryker-html-reporter (#688)

Updates the requirements on [bootstrap](https://github.com/twbs/bootstrap) to permit the latest version.
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](https://github.com/twbs/bootstrap/commits/v4.1.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
stryker-mutator/stryker,stryker-mutator/stryker,stryker-mutator/stryker