fix(docs): alert docs - alert management import clarification

[bc-maksym-konohorov]

Slightly changed docs for Alerts page.

Added some information regarding how to use createAlertsManager instance:

Changed code in CodeSnippet to be string, as it didn't render correctly, in was rendering extra } character, which could confuse consumers of this example:

[jdschmitt]

This is a great update @bc-maksym-konohorov. As a consumer of BigDesign, this does make it more clear for me. Thanks for taking the time to improve our docs!

[deini]

We should prob investigate the extra } you are mentioning.

[bc-maksym-konohorov]

My suggestion - jsx-to-string transformer works in a weird way, it depends on indentation in code, I moved two closing curly braces }} back, and it rendered it right. but there was a problem when you add just regular js code line before function. it rendered it incorrectly, and also linter on commit hook was breaking formatting.

[deini]

Maybe we should add an example on how to create a useAlerts hook.

[bc-maksym-konohorov]

Agree it's a good idea, but I need to play with hook to become familiar with it, and unfortunately I'm not sure If I will have time for that in this sprint.