Update list of performance improvement tips

[cadamini]

An attempt to improve the texts of the bullet points and to shorten this long list.

Description:

This improves the list that grew from version 0.0.x to 1.3.0

Changes proposed:

• general tips on top in the intro
• improved texts in the list
• two separate lists for general and specific use cases
• better readability

Note: I was unsure if we should apply a certain order to the list items. I am not familiar with a-frame.

[dmarcos]

Thanks! Re-wording is usually a matter of voice consistency and taste. Are there any additions you want to make or just reorganization?

[cadamini]

I have not worked with a-frame at all.It is just the reorg, not more.

[dmarcos]

Thanks. I think I like the simplicity of a single list of tips. Have you had any issues understanding or following the guidelines when building something?

[cadamini]

I like the simplicity of a single list of tips

Fair enough. Just tried to make things more readable. It's a single list again.

Have you had any issues understanding or following the guidelines when building something?

Nope. I have no experience at all. Just came across your documentation when I tried to answer an SO question. Found this list and thought that it could be improved.

No worries. If you're not happy, you can still close this PR and everything's remains the same.