feat(eslint-config): use `eslint>=7` as peerDependency

[splincode]

What kind of change does this PR introduce?

• [ ] Bugfix
• [x] Feature
• [ ] Refactoring
• [ ] Code style update
• [ ] Build or CI related changes
• [ ] Documentation content changes

What is the new behavior?

Users can install manually eslint 8 as optional package instead of transitive dependency