Update optional leaflet dependency to (latest) stable version

[Thijss]

Description of changes

The optional leaflet dependency currently points to a release candidate.
To me, it seems better to point to a stable release instead.
Coincidentally, dash-leaflet 1.1.* was released today.

Note: dash-leaflet 1.1.0 had an issue (see here), so I set the minimal requirement to 1.1.1

Pre-Merge checklist

• The project was correctly built with npm run build:all.
• If there was any conflict, it was solved correctly.
• All changes were documented in CHANGELOG.md.
• All tests on CircleCI have passed.
• All Percy visual changes have been approved.
• At least one person has 💃'd the pull request.

Closes #220

Other comments

Python version

The miminum python requirement for dash-leaflet is now >3.12, while for dash-cytoscape it is python_requires=">=3.8"
Might be a good idea to start updating the minimum python version of dash-cytoscape too. For example, python 3.8 has already reached end-of-life (https://devguide.python.org/versions/)

In my experience, supporting the latest 3 stable versions (3.12, 3.13, 3.14) is a good practice

[Thijss]

All changes were documented in CHANGELOG.md.

Is this an automatic process or do I need to update CHANGELOG.md manually?