Emoji deprecation warning

[BalzaniEdoardo]

This Pull request updates the emoji logic for mkdocs-material, fixes #103.

• I completed the issue numbers (#xx) in the sentence above. The word "fixes" should remain in front of each issue
• My PR is tagged as draft when I'm still working on it, and I remove the draft flag when it is ready for review.
• I added one or several changelog.md entries in the appropriate "in progress" section (not the last release one)

b - My PR fixes some issues:

• Each issue is well-described, well-labeled, and contains reproducible code examples.

[BalzaniEdoardo]

Sorry about the tests failing, I didn't have python 3.7 installed locally.
I checked the python support of mkdocs-material, and they need python >=3.8. What should I do about this?

[BalzaniEdoardo]

Thanks for the guidance!

[smarie]

Thanks a lot @BalzaniEdoardo !