[Snyk] Upgrade tslib from 2.8.0 to 2.8.1

[jumpinjackie]

Snyk has created this PR to upgrade tslib from 2.8.0 to 2.8.1.

:information_source: Keep your dependencies up-to-date. This makes it easier to fix existing vulnerabilities and to more quickly identify and fix newly disclosed vulnerabilities when they affect your project.

---

• The recommended version is 1 version ahead of your current version.

• The recommended version was released on 6 days ago.

---

[!IMPORTANT]

• Check the changes in this PR to ensure they won't cause issues with your project.
• This PR was automatically created by Snyk using the credentials of a real user.

---

Note: You are seeing this because you or someone else with access to this repository has authorized Snyk to open upgrade PRs.

For more information:

• 🧐 View latest project report
• 📜 Customise PR templates
• 🛠 Adjust upgrade PR settings
• 🔕 Ignore this dependency or unsubscribe from future upgrade PRs

[coveralls]

coverage: 64.24%. remained the same when pulling b6da9656f94cae00e9824b75f5d62a125a5fb214 on snyk-upgrade-f2465ddc98a646e0676693fb5f042c49 into 99ee08c424a9b3c1828caa24b3a12928ed4eeeaf on master.