title: file parameter in declarative pipeline
body: <p>I am developing declarative pipeline and want to use file parameter to read its content, but its not working as expected</p>
  
  <pre><code>parameters{
          file(fileLocation:'list.txt', description:'contains list of projects to be build')
     }
  </code></pre>
  
  <p>I am getting following error</p>
  
  <pre><code>org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
  WorkflowScript: 12: Invalid parameter "fileLocation", did you mean "description"? @ line 12, column 14.
             file(fileLocation:'release-list.txt', description:'contains list of projects to be build')
  </code></pre>
  
  <p>Following is another option mentioned for basic step plugin</p>
  
  <pre><code>readFile: Read file from workspace
  Reads a file from a relative path (with root in current directory, usually workspace) and returns its content as a plain string.
  file
  Relative ( /-separated) path to file within a workspace to read.
  Type: String
  encoding (optional)
  Type: String
  </code></pre>
  
  <p>its working in script step like</p>
  
  <pre><code>def myfile = readFile('list.txt')
  echo "${myfile}"
  </code></pre>
  
  <p>But how to use it directly in declarative script as we used other basic steps like dir??</p>