Update README.md and metadata.json for 7.1.0-preview.1

[adityapatwardhan]

PR Summary

Update docs for the upcoming release of 7.1.0-preview.1

PR Context

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the title (the WIP bot will keep its status check at Pending while the prefix is present) and remove the prefix when the PR is ready.
• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
    • Experimental feature name(s):
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed:
• Testing - New and feature
  • N/A or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed
• Tooling
  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
  • OR
  • I have considered the user experience from a tooling perspective and enumerated concerns in the summary. This may include:
    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).

[PoshChan]

@TravisEz13, your last commit had 1 failures in PowerShell-CI-linux
Requires tests.Version checks.Check for version 7.1

Expected an exception, with type [System.Management.Automation.ScriptRequiresException] to be thrown, but no exception was thrown.
at <ScriptBlock>, /home/vsts/work/1/s/test/powershell/Language/Scripting/Requires.Tests.ps1: line 90
90:             { . $File } | Should -Throw -ExceptionType ([System.Management.Automation.ScriptRequiresException])

[ghost]

🎉v7.1.0-preview.2 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes