title: How to add and install peer dependencies in Angular library
body: <p>Now I am building Angular library for defining reusable components.
  I made a component named main-layout.
  I needed to use ngx-perfect-scrollbar in the component.
  I know how to add dependencies in Angular project.</p>
  
  <pre><code>ng add [package name]
  </code></pre>
  
  <p>or</p>
  
  <pre><code>npm install [package name]
  </code></pre>
  
  <p>But I saw an article that says peer dependencies are added manually.
  so I added ngx-perfect-scrollbar in peerDependencies on package.json of the library I am developing.</p>
  
  <p><a href="https://i.stack.imgur.com/4Xuw9.png" rel="noreferrer"><img src="https://i.stack.imgur.com/4Xuw9.png" alt="enter image description here"></a></p>
  
  <p>After that, I tried to install npm packages in the root of the project.</p>
  
  <pre><code>npm install
  </code></pre>
  
  <p>then I noticed that ngx-perfect-scrollbar package did not be installed in node_modules.</p>
  
  <p>Below is the full structure of my angular library project.</p>
  
  <p><a href="https://i.stack.imgur.com/Q5XtO.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Q5XtO.png" alt="enter image description here"></a></p>