Bump bootstrap-vue from 2.0.0-rc.11 to 2.0.0-rc.12 in /html

Bumps [bootstrap-vue](https://github.com/bootstrap-vue/bootstrap-vue) from 2.0.0-rc.11 to 2.0.0-rc.12.
- [Release notes](https://github.com/bootstrap-vue/bootstrap-vue/releases)
- [Changelog](https://github.com/bootstrap-vue/bootstrap-vue/blob/dev/CHANGELOG-OLD.md)
- [Commits](bootstrap-vue/bootstrap-vue@v2.0.0-rc.11...v2.0.0-rc.12)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]