Update .npmignore file

[Turbo87]

npm notice 📦  ember-cli-htmlbars-inline-precompile@1.0.5
npm notice === Tarball Contents ===
npm notice 2.4kB   package.json
npm notice 8.7kB   CHANGELOG.md
npm notice 5.8kB   index.js
npm notice 1.1kB   LICENSE.md
npm notice 5.7kB   README.md
npm notice 312.9kB yarn.lock
npm notice 90B     config/environment.js
npm notice 3.6kB   lib/ast-plugins.js
npm notice 1.3kB   lib/require-from-worker.js
npm notice 84B     node-tests/fixtures/compiler.js
npm notice 1.1kB   node-tests/purge-module-test.js
npm notice 10.4kB  node-tests/test.js
npm notice === Tarball Details ===
npm notice name:          ember-cli-htmlbars-inline-precompile
npm notice version:       1.0.5
npm notice package size:  120.8 kB
npm notice unpacked size: 353.0 kB
npm notice shasum:        312e050c9e3dd301c55fb399fd706296cd0b1d6a
npm notice integrity:     sha512-/CNEqPxroIcbY[...]uK4vFFJpkGqkQ==
npm notice total files:   12

This PR drops the unnecessary node-tests files and most of all the yarn.lock file from the distributed npm package