Update CMake README.md

[aepanchi]

Description

A bunch of grammar and style fixes; add an example.

Fixes # - issue number(s) if exists

• - git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details)

Type of change

Choose one or multiple, leave empty if none of the other choices apply

Add a respective label(s) to PR if you have permissions

• bug fix - change that fixes an issue
• new feature - change that adds functionality
• tests - change in tests
• infrastructure - change in infrastructure and CI
• documentation - documentation update

Tests

• added - required for new features and some bug fixes
• not needed

Documentation

• updated in # - add PR number
• needs to be updated
• not needed

Breaks backward compatibility

• Yes
• No
• Unknown

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Other information

[omalyshe]

LGTM.