chore(NODE-6488): specify target=es2021 for ts compilation tests

[baileympearson]

Description

What is changing?

Set target to es2021 to avoid errors related to supporting JS syntax below our lowest supported node version.

Is there new documentation needed for these changes?

Yes, added to the readme

What is the motivation for this change?

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[nbbeeken]

I went to leave a bit of breadcrumb in the PR description and when I got to the "documentation?" question is made me think that maybe we should update our "Typescript Version" section with this change. We say we support 4.4 but now we're specifically saying we support 4.4 with a target later than es2021 right?

If we introduced a private field like the node types did, our tests would pass, but anyone not using this target or later would no longer be able to compile with our types, just as we weren't able to with the node type changes, right?

[baileympearson]

I went to leave a bit of breadcrumb in the PR description and when I got to the "documentation?" question is made me think that maybe we should update our "Typescript Version" section with this change. We say we support 4.4 but now we're specifically saying we support 4.4 with a target later than es2021 right?

If we introduced a private field like the node types did, our tests would pass, but anyone not using this target or later would no longer be able to compile with our types, just as we weren't able to with the node type changes, right?

Yes, but I think that is fine because that aligns with our runtime behavior. Node16 is the first Node version that supports 100% of es2021. We are free to use 100% of the syntax in es2021 in our codebase (including private fields).

Happy to reconsider though.

[nbbeeken]

You sound confident enough for me! let's just capture the new expectations in the Readme in our 'TS Version' section.

I assume this is a pattern we will follow moving forward right? so when we bump min node version we can also bump the required target to compile?