chore: add missing domains to tilde methods

[elidana]

Hi,
a "tilde method" table was added to support the migration of manually collected volcano monitoring data and preserve what was the "method" description in FITS.
The table is currently missing info for dart and tsunami gauge domains.
@ozym , @salichon would you please be able to provide a short description of the "methods" and reference used for:

• dart, 15s
• dart, 15m
• dart, raw
• coastal, 15s
  and we can add these here

Thanks a lot!

[salichon]

@elidana (me tentative)
a short description of the "methods" and reference used for:

dart, 15s : Water pressure, temperature or height - Paroscientifc Ocean floor sensors
dart, 15m: Tide observations, Water height - Paroscientifc instruments Ocean floor sensors
dart, raw: Water pressure, temperature, Instrument 15s continuous Original recordings converted to Water height - Paroscientifc instruments Ocean floor sensors
coastal, 15s: Water pressure, height - Ocean shores sensors

is it still adequate to do ?

Cheers
erome