docs: update readme to use ESM (#68)

Author: 43081j

README.md

@@ -41,24 +41,24 @@ The primary export of `check-error` is an object which has the following methods
 * `getMessage(err)` - Retrieves the message of an error or `err` itself if it's a String. If `err` or `err.message` is undefined we return an empty String.
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 ```
 
 #### .compatibleInstance(err, errorLike)
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 
-var funcThatThrows = function() { throw new TypeError('I am a TypeError') };
-var caughtErr;
+const funcThatThrows = function() { throw new TypeError('I am a TypeError') };
+let caughtErr;
 
 try {
   funcThatThrows();
 } catch(e) {
   caughtErr = e;
 }
 
-var sameInstance = caughtErr;
+const sameInstance = caughtErr;
 
 checkError.compatibleInstance(caughtErr, sameInstance); // true
 checkError.compatibleInstance(caughtErr, new TypeError('Another error')); // false
@@ -67,10 +67,10 @@ checkError.compatibleInstance(caughtErr, new TypeError('Another error')); // fal
 #### .compatibleConstructor(err, errorLike)
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 
-var funcThatThrows = function() { throw new TypeError('I am a TypeError') };
-var caughtErr;
+const funcThatThrows = function() { throw new TypeError('I am a TypeError') };
+let caughtErr;
 
 try {
   funcThatThrows();
@@ -86,18 +86,18 @@ checkError.compatibleConstructor(caughtErr, RangeError); // false
 #### .compatibleMessage(err, errMatcher)
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 
-var funcThatThrows = function() { throw new TypeError('I am a TypeError') };
-var caughtErr;
+const funcThatThrows = function() { throw new TypeError('I am a TypeError') };
+let caughtErr;
 
 try {
   funcThatThrows();
 } catch(e) {
   caughtErr = e;
 }
 
-var sameInstance = caughtErr;
+const sameInstance = caughtErr;
 
 checkError.compatibleMessage(caughtErr, /TypeError$/); // true
 checkError.compatibleMessage(caughtErr, 'I am a'); // true
@@ -108,37 +108,37 @@ checkError.compatibleMessage(caughtErr, 'I do not exist'); // false
 #### .getConstructorName(errorLike)
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 
-var funcThatThrows = function() { throw new TypeError('I am a TypeError') };
-var caughtErr;
+const funcThatThrows = function() { throw new TypeError('I am a TypeError') };
+let caughtErr;
 
 try {
   funcThatThrows();
 } catch(e) {
   caughtErr = e;
 }
 
-var sameInstance = caughtErr;
+const sameInstance = caughtErr;
 
 checkError.getConstructorName(caughtErr) // 'TypeError'
 ```
 
 #### .getMessage(err)
 
 ```js
-var checkError = require('check-error');
+import * as checkError 'check-error';
 
-var funcThatThrows = function() { throw new TypeError('I am a TypeError') };
-var caughtErr;
+const funcThatThrows = function() { throw new TypeError('I am a TypeError') };
+let caughtErr;
 
 try {
   funcThatThrows();
 } catch(e) {
   caughtErr = e;
 }
 
-var sameInstance = caughtErr;
+const sameInstance = caughtErr;
 
 checkError.getMessage(caughtErr) // 'I am a TypeError'
 ```