Add documentation for LRTS / Pseudo Irregular to RTD

[krowvin]

Is your feature request related to a problem? Please describe.
More documentation regarding LRTS vs Pseudo Irregular

Describe the solution you'd like
Add documentation explaining, some of this history (why), and how/what is used for the LRTS vs Pseudo irregular

https://cwms-data-api.readthedocs.io/latest/endpoints/timeSeries_endpoints/timeseries_basics.html#timeseries-basics

Possibly pull the docs out of Confluence? Confluence might be public, we could possibly link to there too?

Additional context
Brought up during the 06/29/2026 CDA BiWeekly call

[rma-psmorris]

Consider adding a note or callout to this documentation that configuration, properties, scripts that define LRTS as strings will need to be updated to use the proper LocalRegular interval independent of the CWMS switches that govern usage of ~Regular vs LocalRegular intervals, ex: ~Hour vs 1HourLocalRegular