Update the LFE Style Guide

[oubiwann]

Tasks:

• Migrate the old style guide content into the new dev site - Deprecate style guide on site in favour the LFE Style Guide book #101
• Style Guide: Add Content to 6 Testing - Style Guide: Add Content to 6 Testing #6
• Style Guide: Add Content to 7.3 Objects and State - Style Guide: Add Content to 7.3 Objects and State #7
• Style Guide: Add Content to 8.2 EVAL-WHEN-COMPILE - Style Guide: Add Content to 8.2 EVAL-WHEN-COMPILE #8
• Style Guide: Add Content to 12 Pitfalls - Style Guide: Add Content to 12 Pitfalls #5

Part of epic #98

[oubiwann]

Do this in guidebook instead.