export default `Limits` and `Timeout`

[calestyo]

Hey.

I've had already stumbled over this in the original httpx, but then it's development had already - let's say diplomatically - "ceased".

AFAICS, it's not possible to generate Limits and/or Timeout, where only certain settings are overwritten, without using "private" API.

The defaults are encoded here:

httpx2/src/httpx2/httpx2/_config.py

Lines 247 to 249 in 70fac53

	DEFAULT_TIMEOUT_CONFIG = Timeout(timeout=5.0)
	DEFAULT_LIMITS = Limits(max_connections=100, max_keepalive_connections=20)
	DEFAULT_MAX_REDIRECTS = 20

but _config is strictly speaking private.

Would be nice if these could be somehow exported, or perhaps simply merged into the __init__-methods of their classes?

Thanks,
Chris.