Safe get symbol function; standardjs removal; package update; code formatting.

[acoelhosantos]

I removed standardjs and formatted the code with prettier. I believe that both have pros/cons that do not need to be discussed here. Since my dev-pipeline uses prettier, I ended up using it here also (maybe it should not have gone in the PR).

Most importantly, I added a new function - safeGetSymbolFromCurrency - to get the symbol or if the lookup fails, return the input as-is. I believe having both options will help whoever uses this package.