Use @backstage/plugin-techdocs-node instead of @backstage/techdocs-common

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

docs/features/techdocs/cli.md

@@ -97,7 +97,7 @@ techdocs-cli generate
 Alias: `techdocs-cli build`
 
 The generate command uses the
-[`@backstage/techdocs-common`](https://github.com/backstage/backstage/tree/master/packages/techdocs-common)
+[`@backstage/plugin-techdocs-node`](https://github.com/backstage/backstage/tree/master/plugins/techdocs-node)
 package from Backstage for consistency. A Backstage app can also generate and
 publish TechDocs sites if `techdocs.builder` is set to `'local'` in
 `app-config.yaml`. See

docs/getting-started/project-structure.md

@@ -160,8 +160,8 @@ are separated out into their own folder, see further down.
   reusable React components. Stories are within the core package, and are
   published in the [Backstage Storybook](https://backstage.io/storybook).
 
-- [`techdocs-common/`](https://github.com/backstage/backstage/tree/master/packages/techdocs-common) -
-  Common functionalities for TechDocs, to be shared between
+- [`techdocs-node/`](https://github.com/backstage/backstage/tree/master/plugins/techdocs-node) -
+  Common node.js functionalities for TechDocs, to be shared between
   [techdocs-backend](https://github.com/backstage/backstage/tree/master/plugins/techdocs-backend)
   plugin and [techdocs-cli](https://github.com/backstage/techdocs-cli).