title: Combine dynamic Github Workflow matrix with input values and predefined values
body: <p>I have a working GitHub workflow that uses a matrix and builds all defined products.</p>
  <pre><code>name: Build
  
  on:
    push:
      tags:
        - &quot;*&quot;
    workflow_dispatch:
  
  jobs:
    build:
      runs-on: ubuntu-latest
      strategy:
        matrix:
         product: [yellow, green, black]
         limits: [10,20,50,100]
  
      steps:
        - uses: actions/checkout@v2
          env:
            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  
      ...
  </code></pre>
  <p>Now a wanted to be able to trigger the build process manually and use input values to only build the product I want. I can enter values on Github interface, but it looks the syntax of using them is not right.</p>
  <blockquote>
  <p>Build : .github#L1 Error when evaluating 'strategy' for job 'build'.
  .github/workflows/build.yml (Line: 27, Col: 18): Unexpected value
  'yellow',.github/workflows/build.yml (Line: 28, Col: 17): Unexpected
  value '50'</p>
  </blockquote>
  <p>Also, how would one combine previous automatic builds of all predefined products with the one manually done via inputs inside one workflow?</p>
  <pre><code>name: Build
  
  on:
    push:
      tags:
        - &quot;*&quot;
    workflow_dispatch:
      inputs:
        product:
          description: &quot;Product&quot;
          default: &quot;yellow&quot;
        limit:
          description: &quot;Limit&quot;
          default: &quot;50&quot;
  
  jobs:
    build:
      runs-on: ubuntu-latest
      strategy:
        matrix:
          product: ${{ github.event.inputs.product}}
          limits: ${{ github.event.inputs.limit }}
  
          # product: [yellow, green, black]
          # limits: [10,20,50,100]
  
      steps:
        - uses: actions/checkout@v2
          env:
            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  
      ...
  </code></pre>