Add icon and add reference in readme and manifest (PowerShell#1291)

* Add icon and add reference in readme and manifest

* correct ratio

* simplify html img tag to auto calculate height

* use square logo

Engine/PSScriptAnalyzer.psd1

@@ -85,7 +85,7 @@ PrivateData = @{
         Tags = 'lint', 'bestpractice'
         LicenseUri = 'https://github.com/PowerShell/PSScriptAnalyzer/blob/master/LICENSE'
         ProjectUri = 'https://github.com/PowerShell/PSScriptAnalyzer'
-        IconUri = ''
+        IconUri = 'https://raw.githubusercontent.com/powershell/psscriptanalyzer/master/logo.png'
         ReleaseNotes = ''
     }
 }

README.md

@@ -1,3 +1,7 @@
+# PSScriptAnalyzer
+
+<img src="logo.png" width="180">
+
 [![Build status](https://ci.appveyor.com/api/projects/status/h5mot3vqtvxw5d7l/branch/master?svg=true)](https://ci.appveyor.com/project/PowerShell/psscriptanalyzer/branch/master) [![Join the chat at https://gitter.im/PowerShell/PSScriptAnalyzer](https://badges.gitter.im/PowerShell/PSScriptAnalyzer.svg)](https://gitter.im/PowerShell/PSScriptAnalyzer?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 Table of Contents