Add npm ci to wasm internal docs (#567)

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- Contributor guidelines followed
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Author: coroiu

crates/bitwarden-wasm-internal/README.md

@@ -12,6 +12,9 @@ contain no logic but rather only handle WASM unique conversions and bindings. Bu
 
 - `wasm32-unknown-unknown` rust target.
 - `binaryen` installed for `wasm-opt` and `wasm2js`.
+- npm packages must be installed in the `npm` folder. Run `npm ci` inside:
+  - **OSS:** `crates/bitwarden-wasm-internal/npm`
+  - **Commercial:** `crates/bitwarden-wasm-internal/bitwarden_license/npm`
 
 ```bash
 rustup target add wasm32-unknown-unknown