Add tidy_near_repeat() function and tests

[mpjashby]

The NearRepeat() function is really useful, but it's hard to use within a pipeline (e.g. using %>% or the new base-R |>) of functions because the inputs must be provided as separate vectors and the output is a nested list of matrices.

I've added a new wrapper around NearRepeat() called tidy_near_repeat() that accepts the input in the form of a data frame or tibble along with the names of the columns containing the x, y and time values.

This function also:

• Identifies the time column in the data automatically if no column is specified and the data contains exactly one Date-type column.
• Extracts the x and y co-ordinates automatically if the data is an SF object and no x and y columns are specified.
• If the co-ordinates are given as longitudes and latitudes, warns users that the values of sds will be interpreted as being in decimal degress.
• Provides default values for the sds and tds arguments.
• Formats the output from NearRepeat() into a tibble that follows the conventions for tidy data.
• Warns users if near repeats are significant for the largest distance or time bands.
• Produces an explanatory message if zero counts mean some Knox ratios could not be calculated.

I've also added tests that cover the inputs and outputs of the functions.