Add CHANGELOG.md for #270.

Also introduces a CHANGELOG.md for the `@apollo/query-planner-wasm` package.

gateway-js/CHANGELOG.md

@@ -5,6 +5,7 @@
 > The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  When a release is being prepared, a new header will be (manually) created below and the appropriate changes within that release will be moved into the new section.
 
 - __BREAKING__: Make all `protected` gateway fields and methods `private` (except `loadServiceDefinitions`). If you currently depend on the ability to override any of these currently `protected` members of `ApolloGateway` please let us know. For additional context on why `loadServiceDefinitions` remains `protected` (for now) please read the associated PR description and linked issue. [PR #539](https://github.com/apollographql/federation/pull/539)
+- deps: `@apollo/query-planner-wasm`: This dependency has been bumped to a version that emits an ECMAScript module (ESM) in addition to the current CommonJS (CJS) bundle.  This may help facilitate interoperability with bundlers thwarted by the presence of the WASM module (`.wasm`) within in this dependency since its inception and included in `@apollo/gateway` since [`v0.20.1`](#v0201).  [PR #270](https://github.com/apollographql/federation/pull/270)  [Issue #255](https://github.com/apollographql/federation/issues/255)
 
 ## v0.23.2
 

query-planner-wasm/CHANGELOG.md

@@ -0,0 +1,7 @@
+# CHANGELOG for `@apollo/query-planner-wasm`
+
+## vNEXT
+
+> The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  When a release is being prepared, a new header will be (manually) created below and the appropriate changes within that release will be moved into the new section.
+
+- To facilitate interoperability with bundlers (e.g., Webpack) attempting to bundle this package which includes a WASM module, we will also now generate a ECMAScript Module (ESM) entry-point for this package _in addition to the existing CommonJS (CJS) bundle.  This new ESM entry-point is conveyed via the [`exports` object within the `package.json`](https://nodejs.org/api/packages.html#packages_exports) of the published package.  It's worth noting that package has always had a WebAssembly (WASM; `.wasm`) module inside of it which was produced with [`wasm-pack`](https://github.com/rustwasm/wasm-pack) but, prior to this change, we'd been specifying the [`--target nodejs`](https://rustwasm.github.io/wasm-pack/book/commands/build.html#target) flag to `wasm-pack build`.  [PR #270](https://github.com/apollographql/federation/pull/270)  [Issue #255](https://github.com/apollographql/federation/issues/255)