Documentation: expand description Api Reference text for imod.formats.ipf.save

[FransRoelofsen]

The IPF file is written based on information in the pandas.DataFrame. Therefore some dataframe columns are required.

Text suggestion:

• df (pandas.DataFrame) – DataFrame containing the data to write. Columns required for X ("x") and Y ("y") coordinates.

in case of itype = 1

• 1 or "timeseries". Columns requires with temporal information ("time")

in case of itype = 2.

• 2 or "borehole1d". Columns required for vertical reference ("top")

in case of itype = 3.

• 3 or "cpt". Columns required for vertical reference ("top")

in case of itype = 4.

• 4 or "borehole3d". Columns required "x_offset", "y_offset", "top"

And what about similar column requirements for imod.formats.ipf.write?

[FransRoelofsen]

in addition:
"top" is defined as the individual top of each Interface described in a single borelog. E.g.

3
2,2
top,1e+20
lithology,1e+20
-1.9,"C"
-2.3,"P"
-4.0,"C"