Hotfix/broadcast wgs84 positions regarding #1036

[andibarg]

I implemented the changes discussed in #1036. This allows us to observe the apparent positions of multiple WGS84 locations on earth with a single line of code and without a for loop.

Example script to validate:

from skyfield.api import load, wgs84, EarthSatellite

ts = load.timescale()
t = ts.now()

planets = load('de440.bsp')
earth = planets['earth']
moon = planets['moon']

ts = load.timescale()
line1 = '1 25544U 98067A   14020.93268519  .00009878  00000-0  18200-3 0  5082'
line2 = '2 25544  51.6498 109.4756 0003572  55.9686 274.8005 15.49815350868473'
satellite = EarthSatellite(line1, line2, 'ISS (ZARYA)', ts)

geopos = wgs84.latlon(latitude_degrees = [0,0],
                      longitude_degrees = [0,10])

# View from moon to geographic positions
pos = moon.at(t).observe(geopos+earth).apparent()
print(pos.xyz)

pos1 = moon.at(t).observe(earth + wgs84.latlon(
    latitude_degrees = 0,
    longitude_degrees = 0,
)).apparent()
print(pos1.xyz)

pos2 = moon.at(t).observe(earth + wgs84.latlon(
    latitude_degrees = 0,
    longitude_degrees = 10,
)).apparent()
print(pos2.xyz)


# View from Satellite to geographic positions
pos = (satellite+earth).at(t).observe(geopos+earth).apparent()
print(pos.xyz)

pos1 = (satellite+earth).at(t).observe(earth + wgs84.latlon(
    latitude_degrees = 0,
    longitude_degrees = 0,
)).apparent()
print(pos1.xyz)

pos2 = (satellite+earth).at(t).observe(earth + wgs84.latlon(
    latitude_degrees = 0,
    longitude_degrees = 10,
)).apparent()
print(pos2.xyz)