Return true if the path is absolute
This function returns true if the path begins with a forward slash ('/').
assert( url_view( "/path/to/file.txt" ).is_path_absolute() );
path = path-abempty ; begins with "/" or is empty
/ path-absolute ; begins with "/" but not "//"
/ path-noscheme ; begins with a non-colon segment
/ path-rootless ; begins with a segment
/ path-empty ; zero characters
path-abempty = *( "/" segment )
path-absolute = "/" [ segment-nz *( "/" segment ) ]
path-noscheme = segment-nz-nc *( "/" segment )
path-rootless = segment-nz *( "/" segment )
path-empty = 0
encoded_path , encoded_segments . path , segments .