Add Julia function reduce

[danlooo]

Use julia function reduce that creates process calls with reduce_dimension to use Julia syntax in openEO transformations.

using Statistics
reduce(*, [2; 3; 4])
#  24
reduce(max, [1,2,3], dims=1)
#1-element Vector{Int64}:
# 3
maximum([1,2,3], dims=1)
#1-element Vector{Int64}:
# 3
max([1,2,3]...)
# 3

In Julia reduce takes an 2-argument function, whereas in openEO, reduce_dimension takes a process with only one argument i.e. data.

[danlooo]

One can now do this:

using OpenEOClient
con = connect("openeocloud.vito.be/openeo", "1.0.0", OpenEOClient.oidc_auth)
cube1 = DataCube(con, "LANDSAT8-9_L2",
    BoundingBox(west=10.8, south=54.1, east=11.6, north=54.5),
    ("2020-01-20", "2020-01-30"), ["B01", "B02", "B03"]
)

cube2 = maximum(cube1["B01"], dims="t")
cube3 = reduce(con.max, cube1["B01"], dims="t")
#openEO DataCube
#   collection: LANDSAT8-9_L2
#   dimensions: ["x", "y"]
#   bands: Unknown
#   spatial extent: nothing
#   temporal extent: nothing
#   license: proprietary
#   connection: https://openeocloud.vito.be/openeo/1.0.0
compute_result(cube3)

[danlooo]

merged see #23