[FR] imrovements to the readme/docs

[ITwrx]

It would be nice if you could add the following answers/topics to the readme and/or docs files.

1. What DBs are supported?
2. Are prepared statements performed automatically?
3. Are queries type checked or checked for correctness or anything?
4. Is all the overhead of the ORM/Query Builder in the compile stage only?
   4a) or is there some runtime overhead?
   4b) if so, what type and how much?
5. What are the performance related features and/or limitations in regards to DB access, per DB supported?

Thanks!

[ITwrx]

Looking at the config example it looks like the answer to 1. is sqlite, mysql and postgresql.

[ITwrx]

my "low level" sql experience is using laravel's eloquent, but it looks like allographer is using placeholders to protect against sql injection, so the answer to number 2 seems to be "yes".

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