docs: make the README Available Data Services entries consistent (#338)

Give every service the same `### Name — `dataretrieval.module`` heading
(Water Use was missing its module reference) and the same
`function: description` bullet style (Water Use listed data categories
instead of its `get_wateruse` getter). Add `get_peaks` to the waterdata
list so peak streamflow appears under the recommended module, not only
under the deprecated NWIS one.


Claude-Session: https://claude.ai/code/session_01Sjb14HkwuCydKSKMsaXsgd

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: thodson-usgs