Add types for polka

[pkuczynski]

Please fill in this template.

• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Add or edit tests to reflect the change. (Run with npm test.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

Select one of these and delete the others:

If adding a new definition:

• The package does not already provide its own types, or cannot have its .d.ts files generated via --declaration
• If this is for an NPM package, match the name. If not, do not conflict with the name of an NPM package.
• Create it with dts-gen --dt, not by basing it on an existing project.
• Represents shape of module/library correctly
• tslint.json should be present and it shouldn't have any additional or disabling of rules. Just content as { "extends": "dtslint/dt.json" }. If for reason the some rule need to be disabled, disable it for that line using // tslint:disable-next-line [ruleName] and not for whole package so that the need for disabling can be reviewed.
• tsconfig.json should have noImplicitAny, noImplicitThis, strictNullChecks, and strictFunctionTypes set to true.

[typescript-bot]

@pkuczynski Thank you for submitting this PR!

Code Reviews

This PR adds a new definition, so it needs to be reviewed by a DT maintainer before it can be merged.

• polka on npm
• polka on unpkg

Status

• ✅ No merge conflicts
• ✅ Continuous integration tests have passed
• ❌ Only a DT maintainer can merge changes when there are new packages added

Once every item on this list is checked, I'll ask you for permission to merge and publish the changes.

---

Diagnostic Information: What the bot saw about this PR

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[pkuczynski]

FYI @JamesMessinger

[typescript-bot]

👋 Hi there! I’ve run some quick measurements against master and your PR. These metrics should help the humans reviewing this PR gauge whether it might negatively affect compile times or editor responsiveness for users who install these typings.

Let’s review the numbers, shall we?

These typings are for a package that doesn’t yet exist on master, so I don’t have anything to compare against yet! In the future, I’ll be able to compare PRs to polka with its source on master.

Comparison details 📊

Batch compilation
Type count	9370
Assignability cache size	3257
Language service measurements
Samples taken	36
Identifiers in tests	36
getCompletionsAtPosition
Mean duration (ms)	316.2
Mean CV	14.5%
Worst duration (ms)	392.2
Worst identifier	routesB
getQuickInfoAtPosition
Mean duration (ms)	316.1
Mean CV	13.6%
Worst duration (ms)	384.9
Worst identifier	middleware
System information
Node version	v12.16.3
CPU count	2
CPU speed	2.394 GHz
CPU model	Intel(R) Xeon(R) CPU E5-2673 v3 @ 2.40GHz
CPU Architecture	x64
Memory	6.8 GiB
Platform	linux
Release	4.15.0-1082-azure

[pkuczynski]

Thanks @sheetalkamat