chore: add trailing-whitespace and end-of-file-fixer to the pre-commit config

.pre-commit-config.yaml

...pentalk-smtp-mailer/resources/templates/common_styles.css

...ntalk-smtp-mailer/resources/templates/header_logo.include

...ests/snapshots/preview__ExternalCancellation-de-Html.snap

...ests/snapshots/preview__ExternalCancellation-en-Html.snap

...iler/tests/snapshots/preview__ExternalInvite-de-Html.snap

...iler/tests/snapshots/preview__ExternalInvite-en-Html.snap

...ts/snapshots/preview__RegisteredCancellation-de-Html.snap

...ts/snapshots/preview__RegisteredCancellation-en-Html.snap

...sts/snapshots/preview__RegisteredEventUpdate-de-Html.snap

...sts/snapshots/preview__RegisteredEventUpdate-en-Html.snap

...er/tests/snapshots/preview__RegisteredInvite-de-Html.snap

...er/tests/snapshots/preview__RegisteredInvite-en-Html.snap

.../tests/snapshots/preview__RegisteredUninvite-de-Html.snap

.../tests/snapshots/preview__RegisteredUninvite-en-Html.snap

.../snapshots/preview__UnregisteredCancellation-de-Html.snap

.../snapshots/preview__UnregisteredCancellation-en-Html.snap

.../tests/snapshots/preview__UnregisteredInvite-de-Html.snap

.../tests/snapshots/preview__UnregisteredInvite-en-Html.snap