Accessibility: Fix View Source and Edit Page icons

[hrahim-moj]

The attached icons do not meet accessibility standards due to their low colour contrast. A ratio of at least 3:! is needed according to the Web Content Accessibility Guidelines

Preferably, we should change the icons to text that simply says 'View Source' and 'Edit This Page'. We could also include this text with the icons but in that case we should still change the colour of them.

[hrahim-moj]

Also consider changing the bottom page icons to text to make them easier to read, or revising their alt-text to make their function apparent.