Update and rename DefaultFileEncoding.md to RFC0020-DefaultFileEncoding.md

added RFC number

Author: SteveL-MSFT

1-Draft/DefaultFileEncoding.md 1-Draft/RFC0020-DefaultFileEncoding.md1-Draft/DefaultFileEncoding.md renamed to 1-Draft/RFC0020-DefaultFileEncoding.md

@@ -1,5 +1,5 @@
 ---
-RFC: Default File Encoding
+RFC: RFC0020
 Author: James Truher
 Status: Draft
 Area: FileSystem
@@ -176,4 +176,4 @@ However, it is somewhat descriptive of our behavior.
 
 ### Alternate Approaches
 The setting need not be a PowerShell variable, it could be an environment variable or part of the configuration proposed by [PowerShell-StartupConfig](https://github.com/PowerShell/PowerShell-RFC/blob/master/1-Draft/RFC0015-PowerShell-StartupConfig.md).
-However, this is the simplest approach and these alternatives can be done at later time.
+However, this is the simplest approach and these alternatives can be done at later time.