fix: add AsyncParser to whatwg export

[joebell1329]

AsyncParser is not currently available from the whatwg package even though the docs suggest it should be https://juanjodiaz.github.io/json2csv/#/parsers/whatwg-async-parser

This PR adds it as an export from the whatwg index.js file.

[coveralls]

Pull Request Test Coverage Report for Build 4344225328

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.888%

---

Totals
Change from base Build 4026331155:	0.0%
Covered Lines:	1408
Relevant Lines:	1432

---

💛 - Coveralls

[joebell1329]

What's the process for getting this published to the NPM repo?

[coveralls]

Pull Request Test Coverage Report for Build 4344225328

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.888%

---

Totals
Change from base Build 4026331155:	0.0%
Covered Lines:	1408
Relevant Lines:	1432

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 4344225328

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.888%

---

Totals
Change from base Build 4026331155:	0.0%
Covered Lines:	1408
Relevant Lines:	1432

---

💛 - Coveralls