👷 Add demo ci workflow

[devtmaz]

Adds sample GitHub Action workflow for learning purposes.

Copilot prompt used to generate workflow:

create for me a yaml configuration for workflow in Github Actions. There are 2 triggers for the workflow: 1. push to main branch. 2. creation of pull request from any branch to main. Action consists of 2 sequential steps: 1. run echo command with text "Command 1", 2. run echo command with text "Command 2"