As a user i want sync local files <> dC workspace

User Story
As a user i want to keep the workspace updated with my files, when for example running periodic syncs (e.g. syncing a database/directory/gh repo content/...)

Option: Synchornizing two states can have quite individual rules to be followed. One solution would be to just implement deletions and users can implement a (simple) script that fits their needs. Additionally we can document this case.

Relevant Links

• we already provide the write_mode (docs) to overwrite files if a file with the same name already exists

Acceptance Criteria

• a user can sync a local directory/list of files with deepset Cloud

### Tasks
- [ ] https://github.com/deepset-ai/deepset-cloud-sdk/issues/112
- [ ] (optional) add sync method that updates existing files and deletes old ones

Start by reading issue #112 and the existing write_mode documentation, since no implementation files or tests are named here. Clarify whether the goal is only local-to-cloud additions or also updates and deletions; the work is done when a local directory or file list can be synchronized with deepset Cloud according to the agreed rules.