fix(package): update @semantic-release/git to version 5.0.0

BREAKING CHANGE: the `GIT_USERNAME` and `GIT_EMAIL` environment variables are replaced by the [Git environment variables](https://git-scm.com/book/en/v2/Git-Internals-Environment-Variables#_committing) `GIT_AUTHOR_NAME`, `GIT_AUTHOR_EMAIL`, `GIT_COMMITTER_NAME` and `GIT_COMMITTER_EMAIL`.

BREAKING CHANGE: the `.gitignore` file is now ignored when adding files to the release commit.
Each files matching a glob in `assets` will now be included in the release commit. The `assets` option has now to be configured to match exactly the the files that have to be committed, independently of the `.gitignore` file.

Author: greenkeeper[bot]

package.json

@@ -19,7 +19,7 @@
     "@semantic-release/changelog": "^2.0.0",
     "@semantic-release/error": "^2.1.0",
     "@semantic-release/exec": "^2.2.0",
-    "@semantic-release/git": "^4.0.0",
+    "@semantic-release/git": "^5.0.0",
     "@semantic-release/github": "^4.2.11",
     "@semantic-release/npm": "^3.2.0",
     "execa": "^0.10.0"