[Arabic] Allah ligature

[moyogo]

The Unicode Standard Version 12.0 page 389 says:

When the formation of the allah ligature is desired, the recommended way to represent the word would be <alef, lam, lam, shadda, superscript alef, heh><0627, 0644, 0644, 0651, 0670, 0647>.

FiraGO currently does not اللّٰه <alef, lam, lam, shadda, superscript alef, heh><0627, 0644, 0644, 0651, 0670, 0647> (doubling the shadda and superscript alef) and other character sequences correctly on the test page https://w3c.github.io/alreq/gap-analysis/tests/ligation/ligation_000.html