update nestjs cjs and index in installation methods

Author: inventarSarah

docs/platforms/javascript/common/install/commonjs-link-quickstart.mdx

@@ -0,0 +1,17 @@
+---
+title: CommonJS (CJS)
+sidebar_order: 9
+description: "Learn about running Sentry in an CJS application."
+supported:
+  - javascript.nestjs
+---
+
+<Alert>
+  Are you unsure if you should use this installation method? Review our
+  [installation methods](../).
+</Alert>
+
+Most node applications today are either written in CommonJS (CJS), or compiled to CJS before running them.
+CommonJS uses `require()` to load modules.
+
+You can find installation instructions for CommonJS in the SDK's <PlatformLink to="/">Quick Start guide</PlatformLink>.

docs/platforms/javascript/common/install/commonjs.mdx

@@ -10,7 +10,6 @@ supported:
   - javascript.hapi
   - javascript.hono
   - javascript.koa
-  - javascript.nestjs
 ---
 
 <Alert>

docs/platforms/javascript/common/install/index.mdx

@@ -41,6 +41,13 @@ CommonJS uses `require()` to load modules. Our recommended installation method w
 
 Note that even if your application is written in ESM (using `import`), it may still be _run_ in CJS. In this case, you should follow the [CommonJS instructions](./commonjs).
 
+<PlatformSection supported={["javascript.nestjs"]}>
+### My application is a simple/default Nest.js app
+
+Nest.js transpiles to CJS by default, so you should follow the [CommonJS installation instructions](./commonjs). Keep reading if you have a more customized application or build setup.
+
+</PlatformSection>
+
 ### My application is in TypeScript
 
 If you're using TypeScript, your application is likely compiled to CommonJS before running it. In this case, you should follow the [CommonJS instructions](./commonjs).