Parser added

[aquatiko]

Port from: https://github.com/astropy/reproject/blob/master/reproject/utils.py
Not a direct port, optimised some methods due to Julia's flexibility.

• Function
• Tests
• Extended Documentation

[aquatiko]

@giordano this PR is completed. Ready for review and merging!!

[aquatiko]

I have made the changes and I'm planning to use it in this way:

function reproject(input_data, output_projection, shape_out = nothing, order = 1, hdu_in = 1, hdu_out = 1, return_footprint = true)
    if input_data isa ImageHDU        # write order functionality, footprint too
        array_in, wcs_out = parse_input_data(input_data)
    else
        array_in, wcs_out = parse_input_data(input_data, hdu_in)
    end
    
    if input_data isa FITS || input_data isa String
        wcs_in, shape_out = parse_output_projection(output_projection, hdu_out)
    else
        wcs_in, shape_out = parse_output_projection(output_projection, shape_out)
    end
end

This way allowed some scope of refactoring, let me know your thoughts on this. Once this is merged, I will push the main body of reproject in a PR.

[giordano]

Only a few minor comments