gitignore: Add personal work files and temporary files

- Ignore .personal_files/ directory for work-in-progress files
- Ignore TESTING_*.md files
- Ignore Windows Zone.Identifier files
- Ignore test backup files

Author: vicky-dx

.gitignore

@@ -158,3 +158,9 @@ crash-*
 corpus*
 libr/anal/d/types-windows.sdb.txt
 libr/bin/d/dll/*.c
+
+# Personal work files
+.personal_files/
+TESTING_*.md
+*:Zone.Identifier
+test/db/cmd/*.backup