[patch] use binary encoding function that does not overflow for qr (#1075)

# Pull Request Template

## Description

If the qr codes get too big (in total file size), then the current
function will blow up. This one works better, tested manually by
updating the dist/build.js, and updating example.html to point to that
instead of the production cdn hosted websdk

I couldnt get this new one to overflow

Fixes # (issue)

## Type of change

Please delete options that are not relevant.

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration

- [ ] Unit test
- [ ] Integration test

## JS Budget Check

Please mention the size in kb before abd after this PR

| Files            | Before      | After       | 
| -----------      | ----------- | ----------- |
| dist/build.js.   |             |             |
| dist/build.min.js|             |             |

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules
- [ ] I have checked my code and corrected any misspellings

## Mentions: 
List the person or team responsible for reviewing proposed changes.

cc @BranchMetrics/saas-sdk-devs for visibility.

Author: bredmond5

.gitignore

@@ -35,3 +35,4 @@ dist
 dev
 .nyc_output
 test-results.json
+.idea/

src/6_branch.js

@@ -1340,20 +1340,22 @@ Branch.prototype['qrCode'] = wrap(
 		this._api(
 			resources.qrCode,
 			utils.cleanLinkData(linkData),
-			function(error, rawBuffer) {
-				function QrCode() { }
-
-				if (!error) {
-					QrCode['rawBuffer'] = rawBuffer;
-					QrCode['base64'] = function() {
-						// First Encode array buffer as UTF-8 String, then Base64 Encode
-						if (this['rawBuffer']) {
-							return btoa(String.fromCharCode.apply(null, new Uint8Array(this['rawBuffer'])));
-						}
-						throw Error('QrCode.rawBuffer is empty.');
-					};
-				}
-				return done(error || null, QrCode || null);
+			(error, rawBuffer) => {
+				if (error) return done(error, null);
+
+				const QrCode = {
+					rawBuffer,
+					base64() {
+						if (!this.rawBuffer) throw new Error('QrCode.rawBuffer is empty.');
+						// Encode the Uint8Array to a binary string, then convert to base64
+						const binaryString = Array.from(new Uint8Array(this.rawBuffer))
+							.map(byte => String.fromCharCode(byte))
+							.join('');
+						return btoa(binaryString);
+					}
+				};
+
+				return done(null, QrCode);
 			}
 		);
 	}