Add images to README.md to show cmdlet output.

This commit adds some example output to the README.md, in image format.
This will let prospective users actually see what this module does.

I would have used something smaller than PNG files, but Markdown does
not have anything like the <source> tag.

README.md

@@ -30,6 +30,7 @@ Exchange Online always uses DKIM selectors "selector1" and "selector2".  If a do
 ```powershell
 PS C:\>  Test-MailPolicy fabrikam.com -DkimSelectorsToCheck "selector1","selector2"
 ```
+![MailPolicyExplainer's output when running:  Test-MailPolicy -DkimSelectorsToCheck 'selector1','selector2' microsoft.com](https://raw.githubusercontent.com/rhymeswithmogul/MailPolicyExplainer/main/man/en-US/Microsoft.com.png)
 
 But what if they *do* use something like Constant Contact?  Assuming the DKIM selector name is known:
 ```powershell
@@ -48,6 +49,9 @@ Or, if you only want to test one aspect of email, you can test items individuall
 PS C:\>  Test-MtaStsPolicy adatum.com
 ```
 
+![MailPolicyExplainer's output when running:  Test-MaStsPolicy colincogle.name](https://raw.githubusercontent.com/rhymeswithmogul/MailPolicyExplainer/main/man/en-US/MyMtaSts.png)
+
+
 ## SPF DNS Lookup Counts
 It can also count how many DNS lookups are in an SPF record.
 ```powershell
@@ -56,6 +60,8 @@ PS C:\>  Test-SpfRecord  northwindtraders.com -CountDnsLookups     # or
 PS C:\>  Test-SpfRecord  northwindtraders.com -Recurse
 ```
 
+![MailPolicyExplainer's output when running:  Test-SpfRecord -Recurse microsoft.com](https://raw.githubusercontent.com/rhymeswithmogul/MailPolicyExplainer/main/man/en-US/MicrosoftSPF.png)
+
 
 # Further Help
 For more help, why not start with [the conceptual help](https://github.com/rhymeswithmogul/MailPolicyExplainer/blob/main/man/en-US/about_MailPolicyExplainer.md)?