fix Test-CredentialStoreItem return (#66)

#### 📖 Summary

- `Test-CredentialStoreItem` now returns `$false` and not a terminating error if store doesn't exists.
- Updates platyPS generated docs

#### 📑 Test Plan

> 💡 Select your test plan for the code changes.

- [x] Tested via Drone.io pipeline
- [ ] Custom test
- [ ] No test plan

##### Details / Justification

<!-- Add your test details or justification for missing tests here. -->

#### 📚 Additional Notes

- fixes #50

Co-authored-by: OCram85 <marco.blessing@googlemail.com>
Reviewed-on: OCram85/PSCredentialStore#66

src/Item/Test-CredentialStoreItem.ps1

@@ -7,6 +7,10 @@ function Test-CredentialStoreItem {
         Use this cmdlet for basic checks with a single item. Check the item first with this function before
         you try to interact with it.
 
+        Breaking Change for `v1.1.0+`:
+        Test-CredentialStoreItem will return `$false` even if the store doesn't exist. We removed the terminating
+        error and replaced it with a warning message.
+
     .PARAMETER Path
         Define a custom credential store you try to read from. Without the `-Path` parameter
         `Test-CredentialStoreItem` tries to read from the default private store.
@@ -88,10 +92,10 @@ function Test-CredentialStoreItem {
         }
         else {
             $MsgParams = @{
-                ErrorAction = 'Stop'
-                Message     = "The given credential store ({0}) does not exist!" -f $Path
+                Message = "The given credential store ({0}) does not exist!" -f $Path
             }
-            Write-Error @MsgParams
+            Write-Warning @MsgParams
+            return $false
         }
     }