GH-47738: [R] Update NEWS.md for 22.0.0 (#47739)

### Rationale for this change

Summarise changes for release

### What changes are included in this PR?

Update NEWS file

### Are these changes tested?

No

### Are there any user-facing changes?

No
* GitHub Issue: #47738

Authored-by: Nic Crane <thisisnic@gmail.com>
Signed-off-by: Raúl Cumplido <raulcumplido@gmail.com>

Author: thisisnic

r/NEWS.md

@@ -19,6 +19,14 @@
 
 # arrow 21.0.0.9000
 
+## New features
+
+- `stringr::str_replace_na()` binding implemented (#47521).
+
+##  Minor improvements and fixes
+
+- Subsecond time variables no longer truncated in  `hms::hms()` bindings (#47278)
+
 # arrow 21.0.0.1
 
 ##  Minor improvements and fixes