chore(package): update @types/chai to version 4.2.9
chore(package): update @types/chai to version 4.2.9

Merge pull request #671 from opensheetmusicdisplay/greenkeeper/@types/chai-4.2.9
opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay