Add an article to introduce preinstrumented jars

[utzcoz]

From Robolectric 4.6, the preinstrumented jars are used by Robolectric default. But the article/post to introduce this big improvement is missing. It's better if we can append this content to our blog, and introduce the internal of preinstrumented jars and its improvement for Robolectric.

[utzcoz]

Hi @hoisie , do you have time to write an article for this topic? I think it can show performance boost of Robolectric after preinstrumented jars introduced.

[MGaetan89]

@utzcoz does #305 (or the existing ARCHITECTURE.md) resolve this issue?

[utzcoz]

@MGaetan89 Yeah. If the architecture page is merged, I think this issue can be closed.

[utzcoz]

Actually I still hope we can have a summary article for recent years' optimization for performance, and many developers can know them from the article. But the architecture documentation is good enough to me now.

[MGaetan89]

Actually I still hope we can have a summary article for recent years' optimization for performance, and many developers can know them from the article. But the architecture documentation is good enough to me now.

Let's keep this open then. For now, the new architecture page will serve as a base, but we can iterate over it later to provide more details and insights.