GH-44518: [R] Update NEWS for 18.0.0 (#44520)

### Rationale for this change

Update NEWS for release

### What changes are included in this PR?

Update NEWS for release

### Are these changes tested?

No

### Are there any user-facing changes?

No
* GitHub Issue: #44518

Authored-by: Nic Crane <thisisnic@gmail.com>
Signed-off-by: Bryce Mecum <petridish@gmail.com>

Author: thisisnic

r/NEWS.md

@@ -19,6 +19,16 @@
 
 # arrow 18.0.0
 
+## Minor improvements and fixes
+
+* Fix bindings to allow filtering a factor column in a Dataset using `%in%` (#43446)
+* Update `str_sub` binding to properly handle negative `end` values (@coussens, #44141)
+* Fix summarize() performance regression (pushdown) (#43649)
+* Fix altrep string columns from readr (#43351)
+* Fix crash in ParquetFileWriter$WriteTable and add WriteBatch (#42241)
+* Fix bindings in Math group generics (@aboyoun, #43162)
+* Fix pull on a grouped query returns the wrong column (#43172)
+
 # arrow 17.0.0
 
 ## New features