title: Typescript cannot find type in definition file in node_modules folder
body: <p>I have a project which has this structure:</p>
  
  <pre><code>project/
  ├── package.config
  ├── node_modules/
  │   ├── interactjs/
  │   ├── ├── index.d.ts
  ├── src/
  │   ├── browser/
  │   |   ├── tsconfig.json
  │   |   ├── index.ts
  </code></pre>
  
  <p>I have the following <code>./package.json</code>:</p>
  
  <pre><code>{
      ...
      "dependencies": {
          "interactjs": "1.3.4"
      },
      "devDependencies": {
          "typescript": "3.2.2"
      }
  }
  </code></pre>
  
  <p>My <code>./src/browser/tsconfig.json</code> is:</p>
  
  <pre><code>{
      "compilerOptions": {
          "target": "es5",
          "module": "none",
          "declaration": true,
          "strict": true,
          "strictNullChecks": false,
          "outDir": "./out"
      },
      "typeRoots": [
          "../../node_modules",
          "../../node_modules/@types",
          "../definitions"
      ],
      "include": [
          "./**/*"
      ]
  }
  </code></pre>
  
  <p>As you can see I am including also folder <code>definitions</code> as there are some manual definitions I want to include in all Typescript files of my project.</p>
  
  <h3>Problem</h3>
  
  <p>The following fails compilation:</p>
  
  <pre><code>const p : interact.Position = { x: 1, y: 2 };
  </code></pre>
  
  <p>With error:</p>
  
  <pre><code>index.ts:9:11 - error TS2503: Cannot find namespace 'interact'.
  
  9 const s : interact.Position = { x: 1, y: 2 };
              ~~~~~~~~
  </code></pre>
  
  <p><code>interact</code> is not found even though in <code>node_modules/interactjs</code> file <code>index.d.ts</code> is present with all the definitions.</p>
  
  <p>What is the problem?</p>