Add ignores for npm publish

[andyrichardson]

Fix #35

Included files:

npm notice 2.5kB  package.json
npm notice 1.1kB  LICENSE
npm notice 1.1kB  README.md
npm notice 89B    tsconfig.exchange.json
npm notice 241B   tsconfig.json
npm notice 1.9kB  dist/exchange.js
npm notice 1.6kB  docs/Development.md
npm notice 238B   src/codemirror.d.ts
npm notice 2.2kB  src/exchange.ts
npm notice 118B   src/globals.d.ts
npm notice 768B   src/styled-components.d.ts
npm notice 697B   src/types.ts