BRE-40 Add step to report upcoming release version to Slack

[urbinaalex17]

Type of change

- [ ] Bug fix
- [] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [X] Build/deploy pipeline (BRE)
- [ ] Other

Objective

Report upcoming release to Slack using the generate version bump by the workflow.

Related PR: bitwarden/gh-actions#281

Code changes

• .github/workflows/version-bump.yml: Add step to report upcoming release

Before you submit

• Please check for formatting errors (dotnet format --verify-no-changes) (required)
• If making database changes - make sure you also update Entity Framework queries and/or migrations
• Please add unit tests where it makes sense to do so (encouraged but not required)
• If this change requires a documentation update - notify the documentation team
• If this change has particular deployment requirements - notify the DevOps team

[bitwarden-bot]

Checkmarx One – Scan Summary & Details – a88953d1-2272-46d9-bcc4-04b9df015c38

New Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Unpinned Actions Full Length Commit SHA	/version-bump.yml: 198	Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps...