## Add firestore-update-document tool
Adds a new tool for updating existing documents in Firestore
collections.
__What it does:__
- Updates documents at any path in Firestore
- Supports partial updates with field masks for selective field
modification
- Handles all Firestore data types (strings, numbers, booleans,
timestamps, geopoints, arrays, maps, etc.)
- Supports field deletion using updateMask
- Uses Firestore's native JSON format for type safety
- Can update nested fields within maps using dot notation
__Key parameters:__
- `documentPath`: The path of the document to update
- `documentData`: The document content in Firestore JSON format
- `updateMask`: Optional array of field paths for selective updates
- `returnData`: Optional flag to include updated document in response
__Special features:__
- When `updateMask` is provided, only specified fields are updated
- Can access nested fields with dot notation (e.g., 'address.city',
'user.profile.name')
- Without updateMask, performs a merge operation updating all provided
fields
