Add README

Author: andrewbranch

packages/history/README.md

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+# @arethetypeswrong/history
+
+This package provides `@arethetypeswrong/core` analysis for every [npm-high-impact](https://github.com/wooorm/npm-high-impact) package at the latest version available on the first of every month since January 2022.
+
+The analysis is saved as a 1.2 GB newline-delimited JSON file, cached in Azure Storage for incremental updates going forward, compressed down to 34 MB for shipping to npm, and accessible in Node as a JavaScript object via a small programmatic interface.
+
+## Usage
+
+```ts
+import { getAllDataAsObject, getVersionsByDate } from "@arethetypeswrong/history";
+
+const dates = await getVersionsByDate();
+const data = await getAllDataAsObject();
+
+function getPackagesWithFalseCJSProblems(date) {
+  const packages = dates[date];
+  const result = [];
+  for (const { packageName, packageVersion } of packages) {
+    const analysis = data[`${packageName}@${packageVersion}`];
+    // `analysis` is undefined if the package doesn't contain types
+    if (analysis?.problems.some((p) => p.kind === "FalseESM")) {
+      result.push(analysis);
+    }
+  }
+  return result;
+}
+
+const mayFalseESMProblems = getPackagesWithFalseCJSProblems("2023-05-01").length;
+const juneFalseESMProblems = getPackagesWithFalseCJSProblems("2023-06-01").length;
+console.log({ mayFalseESMProblems, juneFalseESMProblems });
+```