Improve graphic styling of donate

donate/blocks.py

donate/constants.py

donate/migrations/0028_donatehomepage_faq_page.py

donate/models.py

donate/static/donate/assets/css/style.css

donate/templates/donate/base.html

donate/templates/donate/blocks/custom_content_block.html

donate/templates/donate/donate_home_page.html

donate/templatetags/__init__.py

donate/templatetags/donate_tags.py

donate/wagtail_hooks.py