Improve NEWS entry

Author: thatch

Misc/NEWS.d/next/Library/2017-12-30-18-21-00.bpo-28494.Dt_Wks.rst

@@ -1,13 +1,13 @@
-Improve zipfile validation in `zipfile.is_zipfile`.
+Improve Zip file validation in :func:`zipfile.is_zipfile`.
 
-Before this change `zipfile.is_zipfile()` only checked the End Central Directory
+Before this change :func:`zipfile.is_zipfile` only checked the End Central Directory
 signature.  If the signature could be found in the last 64k of the file,
-success!  This produced false positives on any file with `'PK\x05\x06'` in the
+success!  This produced false positives on any file with ``'PK\x05\x06'`` in the
 last 64k of the file - including PDFs and PNGs.
 
 This is now corrected by actually validating the Central Directory location
-and size based on the information provided by the End Central Directory
+and size based on the information provided by the End of Central Directory
 along with verifying the Central Directory signature of the first entry.
 
-This should be sufficient for the vast number of zipfiles with fewer
+This should be sufficient for the vast number of Zip files with fewer
 false positives.