[Security] Bump atob from 2.0.3 to 2.1.2 (#153)

Bumps [atob](https://github.com/coolaj86/node-browser-compat) from 2.0.3 to 2.1.2. **This update includes security fixes.**
<details>
<summary>Vulnerabilities fixed</summary>

*Sourced from [The Sonatype OSS Index](https://ossindex.sonatype.org/vuln/e391a58d-4a81-448b-8ffc-e19016807d73).*

> **CWE-125: Out-of-bounds Read**
> The software reads data past the end, or before the beginning, of the intended buffer.
> 
> Affected versions: <=2.0.3

*Sourced from [The Node Security Working Group](https://github.com/nodejs/security-wg/blob/master/vuln/npm/403.json).*

> **Out-of-bounds Read**
> `atob` allocates uninitialized Buffers when number is passed in input on Node.js 4.x and below
> 
> Affected versions: <=2.0.3

</details>
<details>
<summary>Commits</summary>

- See full diff in [compare view](https://github.com/coolaj86/node-browser-compat/commits)
</details>
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package-lock.json

@@ -670,9 +670,9 @@
       "integrity": "sha1-x57Zf380y48robyXkLzDZkdLS3k="
     },
     "atob": {
-      "version": "2.0.3",
-      "resolved": "https://registry.npmjs.org/atob/-/atob-2.0.3.tgz",
-      "integrity": "sha1-GcenYEc3dEaPILLS0DNyrX1Mv10="
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/atob/-/atob-2.1.2.tgz",
+      "integrity": "sha512-Wm6ukoaOGJi/73p/cl2GvLjTI5JM1k/O14isD73YML8StrH/7/lRFgmg8nICZgD3bZZvjwCGxtMOD3wWNAu8cg=="
     },
     "autoprefixer": {
       "version": "7.2.6",