Example for commit-message template in CONTRIBUTING.md

[Parikshit-Hooda]

Is your feature request related to a problem? Please describe.
It took me time to find an example commit-message when I was making my first commit to this repo.

Describe the solution you'd like
An example commit-message in CONTRIBUTING.md would be nice under the 'commit message format' section

Describe alternatives you've considered
none.

Additional context
I intend to copy the one already present and being used in webpack-dev-middle contributing file

[webpack-bot]

This issue had no activity for at least half a year.

It's subject to automatic issue closing if there is no activity in the next 15 days.

[alexander-akait]

Done #1364