I have nothing to do with Mozilla's add-ons being 20 years old.
What I know is that I update the GB speller every month.
You have the most up to date British speller, when the other speller was abandoned in 2006.
If you find missing words, just e-mail them to me, and, if they are in Oxford or Collins dictionaries, I will add them.
It is not possible to learn from Google suggestions since spellers only have a file with words and a file with affixes to be applied to the words file (it is impossible for me to add menus and such, as it only checks spelling).
I have just added:
48903) laddu + laddoo + ladoo (+plural +'s)
48904) flipboard (+plural +'s - Collins)
"awesomesauce" is a US word according to Oxford and Cambridge dictionaries, so I didn't add it.
In the future, suggest words via e-mail and not by rating my speller 1 star.