Added '.js' extension to ES6 import

src/asciimath-to-tex.spec.js

@@ -1,5 +1,5 @@
 import test from 'ava';
-import asciimathToTex from './asciimath-to-tex';
+import asciimathToTex from './asciimath-to-tex.js';
 
 test('just a number', t => {
   t.is(asciimathToTex('5'), '{5}');

src/showdown-katex.js

@@ -1,7 +1,7 @@
 import katex from 'katex';
-import renderMathInElement from 'katex/dist/contrib/auto-render';
+import renderMathInElement from 'katex/dist/contrib/auto-render.js';
 import showdown from 'showdown';
-import asciimathToTex from './asciimath-to-tex';
+import asciimathToTex from './asciimath-to-tex.js';
 
 if (process.env.TARGET === 'cjs') {
   const { JSDOM } = require('jsdom');

src/showdown-katex.spec.js

@@ -1,6 +1,6 @@
 import test from 'ava';
 import showdown from 'showdown';
-import katex from '../lib/showdown-katex';
+import katex from '../lib/showdown-katex.js';
 
 const input = '# hello, markdown!';
 const output = '<h1 id="hellomarkdown">hello, markdown!</h1>';