chore: add script for generating release notes

[web-padawan]

Description

Added the script to generate release notes (based on the one from web components repository with some cleanup).

Example output that I already used for 1.0.0-alpha.3 release notes:

$ node ./scripts/generateReleaseNotes.js
### Changes Since [v1.0.0-alpha.2](https://github.com/vaadin/eslint-config-vaadin/releases/tag/v1.0.0-alpha.2)

#### :bug:　Bug Fixes
- [`76b3cbf`](https://github.com/vaadin/eslint-config-vaadin/commit/76b3cbf) Add missing ./index entrypoint to package exports ([#21](https://github.com/vaadin/eslint-config-vaadin/pull/21))

#### :nail_care:　Polish
- [`bf58e6a`](https://github.com/vaadin/eslint-config-vaadin/commit/bf58e6a) Rename index.js to javascript.js ([#22](https://github.com/vaadin/eslint-config-vaadin/pull/22))

#### :house:　Internal
- [`e7c582d`](https://github.com/vaadin/eslint-config-vaadin/commit/e7c582d) Update documentation in README.md ([#24](https://github.com/vaadin/eslint-config-vaadin/pull/24))
- [`509bf20`](https://github.com/vaadin/eslint-config-vaadin/commit/509bf20) Add javascript.js to .gitignore ([#23](https://github.com/vaadin/eslint-config-vaadin/pull/23))
- [`31934e8`](https://github.com/vaadin/eslint-config-vaadin/commit/31934e8) Update documentation in README.md ([#20](https://github.com/vaadin/eslint-config-vaadin/pull/20))

Type of change

• Internal change