feat: new rule scalar-property-missing-example

[RomanHotsiy]

What/Why/How?

This is a useful rule to ensure every scalar property has an example defined.

Reference

Slack discussion: https://redoc-ly.slack.com/archives/C02UHE7EL3E/p1653357899168609

Testing

TODO

Screenshots (optional)

Check yourself

• Code is linted
• Tested with redoc/reference-docs/workflows
• All new/updated code is covered with tests

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

[github-actions]

Coverage report

Total coverage

Status	Category	Percentage	Covered / Total
🟡	Statements	65.92%	2636/3999
🟡	Branches	60.01%	1445/2408
🔴	Functions	57.79%	419/725
🟡	Lines	66.16%	2438/3685

Status of coverage: 🟢 - ok, 🟡 - slightly more than threshold, 🔴 - under the threshold

Show new covered files 🌑

Coverage of new files

Status	Filename	Statements	Branches	Functions	Lines
🟢	home/runner/work/redocly-cli/redocly-cli/packages/core/src/rules/common/scalar-property-missing-example.ts	80.95%	80%	75%	84.21%

Status of coverage: 🟢 - ok, 🟡 - slightly more than threshold, 🔴 - under the threshold

Report generated by 🧪jest coverage report action from 47c0cf6

[adamaltman]

🕺