Change icons of Roadmap items

Emojis look different on each device and some can be ugly (for example the check on Chrome appears grey).

The options could be:

• Change emojis
• Use minimal black and white icons (https://icons.getbootstrap.com was pointed out as a possibility)
• Use pics (option that i discarded initially to not make the page heavier)
• https://primer.style/octicons/ (can be integrated with jekyll)

Voice your opinion.