Export @solana/functional from the main library (#2007)

It's wierd for `@solana/functional` to be the only thing that you have to add as a dependency separate from `@solana/web3.js`, if that's the way you're going.

packages/library/src/index.ts

@@ -1,4 +1,5 @@
 export * from '@solana/addresses';
+export * from '@solana/functional';
 export * from '@solana/instructions';
 export * from '@solana/keys';
 export * from '@solana/rpc-types';