[Feature] Airdrop Option

[A91y]

An airdrop option, should be added directly in the playground to increase ease of usability.

[acheroncrypto]

Playground supports automatic airdrops but it was disabled on devnet because of rate limits (#151 (comment)). I believe airdrop limits were increased recently so we may re-enable the feature for devnet.

There is also airdrop option in the wallet but not enabled on devnet for the same reason as above:

Other than the automatic airdrop and manual airdrop from the wallet, you can also run solana airdrop <AMOUNT> command in terminal.