Improve section "Recommended usage patterns" in docs

[IAmNotHanni]

• Use vmaCopyMemoryToAllocation in section "Recommended usage patterns".
• Try to embed the code from the actual test in the docs, so the code which is displayed there is actually tested and compiled.

[adam-sawicki-a]

Agreed, this may be a good idea. However, I am not sure if a code taken from a test would look good in the documentation. Copy-paste with some modifications to improve the readability as a standalone code sample could work better.