Bumped tantivy version to 0.15.3 in Cargo.toml

Hotfix 0.15.2

use github actions for tests

Bumped tantivy version to 0.15

Removing unused imports.

Release 0.13.3

Closes quickwit-oss#896 - Facet reader related

Bugfix. Acquiring a facet reader on a segment that does not contain any
doc with this facet returns `None`.

Bumped version and edited changelog

Bumped version

Merge branch 'master' of github.com:tantivy-search/tantivy