Consistency update for images through-out the Docs.

[Bas02]

After a short talk about consistency, we decided to go with Light mode through out the Docs.

• [x] Go Through User Docs Update images to Lightmode
• [x] Go through Deployment Docs update images to Lightmode
• [x] Go through Developers Docs update images to Lightmode
• [x] Go through Contribute Docs update images to Lightmode
• [x] Main Guide Img update to new GUI done in #1101
• [x] Note missing video's

[Bas02]

Did most of the USER DOCS in PR #1096 Except this list :

• [x] Shopify in Lightmode
• [x] WooCommerce in Lightmode
• [x] Hardware wallet page Lightmode
• [x] Payjoin needs rewriting see issue : #1097