feat: Add support for Node 16, 18, remove support for Node 12, 15

[mtrezza]

• Adds CI tests for Node 14, 16, 18
• Removes CI tests for Node 12, 15

[parse-github-assistant[bot]]

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[parse-github-assistant[bot]]

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[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (7c05af7) 95.72% compared to head (c42c820) 95.72%.

:exclamation: Current head c42c820 differs from pull request most recent head 217ef3b. Consider uploading reports for the commit 217ef3b to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #189 +/- ## ======================================= Coverage 95.72% 95.72% ======================================= Files 2 2 Lines 187 187 Branches 41 41 ======================================= Hits 179 179 Misses 8 8 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community)

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[parseplatformorg]

🎉 This change has been released in version 2.0.0