Bugfix: Keymap 3D view

Description of change

Adv. Drawing keymap in userpref.blend:

• Middle Mouse pan the view instead of rotate (shift + MMB to rotate)
• Left click never select something (could lead to exiting GP...)

Fix #249 (closed)

How to test it

• Use Adv. Drawing

Checklist

Please check if your MR fulfills the following requirements:

• Unit tests have been added, if needed
• Documentation have been updated, if needed
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• Package.py have been updated, if needed
• CHANGELOG.md have been updated, if needed
• Version numer has been tagged, if needed

FYI: @awesome_dev_too