normalize_obs: Normalize observations, effort, or times
In weecology/MATSS: Macroecological Analyses of Time Series Structure

normalize_obs will normalize the observations to the provided effort vector, if obs_per_effort is TRUE.

normalize_effort will generate a default effort vector if it is not provided, (effort = 1 over the provided obs time series)

normalize_times will generate a default times vector if it is not provided, (times = seq(length(obs)))

normalize_obs(obs, effort, obs_per_effort = !is.null(effort))

normalize_times(obs, times = NULL)

normalize_effort(obs, effort = NULL)

`obs`	the time series of `numeric` observations
`effort`	`numeric` vector of effort associated with the observations.
`obs_per_effort`	`logical` indicator if `obs` should be corrected for `effort` before summaries are done.
`times`	`numeric` or `Date` vector of timestamps of the observations.