Add code coverage badge via coveralls.

Author: mrseanryan

.nycrc

@@ -11,6 +11,7 @@
     "require": ["ts-node/register"],
     "reporter": [
         "html",
+        "lcov",
         "text",
         "text-summary"
     ],

.travis.yml

@@ -3,3 +3,7 @@ node_js:
   - 10
   - 12
   # TODO - 14 when it is released
+script:
+  - npm test
+after_success:
+  - npm run report-coverage-to-coveralls

README.md

@@ -3,6 +3,7 @@
 `ts-unused-exports` finds unused exported symbols in your Typescript project.
 
 [![Build Status](https://travis-ci.com/pzavolinsky/ts-unused-exports.svg?branch=master)](https://travis-ci.com/pzavolinsky/ts-unused-exports)
+[![Coveralls](https://img.shields.io/coveralls/pzavolinsky/ts-unused-exports.svg)](https://coveralls.io/github/pzavolinsky/ts-unused-exports)
 
 [![Dependencies](https://david-dm.org/pzavolinsky/ts-unused-exports.svg)](https://david-dm.org/pzavolinsky/ts-unused-exports)