Chore: Update .gitignore

- Ignore multiple virtualenvs
- Ignore `tmpdb.sqlite` created by software tests

Author: amotl

.gitignore

@@ -10,8 +10,11 @@ rdflib_sqlalchemy.egg-info
 /.eggs/
 /dist/
 /venv/
+.venv*
 docs/api
 
 # JetBrains IDE files
 /.idea/
 
+# Test outcomes
+test/tmpdb.sqlite