specify files array

[vonovak]

this decreases size of what is shipped

before

npm notice === Tarball Details ===
npm notice name:          react-native-dialogs
npm notice version:       1.1.0
npm notice filename:      react-native-dialogs-1.1.0.tgz
npm notice package size:  635.9 kB
npm notice unpacked size: 741.1 kB
npm notice shasum:        be4592eff4459036ba9a027d21097e4827a214f7
npm notice integrity:     sha512-8vo5allZeuWYA[...]ikosG0ynnT9Zg==
npm notice total files:   24

now

npm notice === Tarball Details ===
npm notice name:          react-native-dialogs
npm notice version:       1.1.0
npm notice filename:      react-native-dialogs-1.1.0.tgz
npm notice package size:  67.2 kB
npm notice unpacked size: 151.1 kB
npm notice shasum:        8f7ee7f9d96574fc878fb7c1be101611fb4af517
npm notice integrity:     sha512-clnxO0nMyML/6[...]0tqV3rcZWUrjQ==
npm notice total files:   13