pester: Add checkver script

* Add checkver script that checks all release tags (similar to `main/pnpm`)
* Pester mixes ver4 and ver5 in their releases. This will prevent the "wrong revert" error preemptively.

bucket/pester.json

@@ -14,7 +14,20 @@
         "name": "Pester"
     },
     "checkver": {
-        "github": "https://github.com/pester/Pester"
+        "script": [
+            "# Using checkver script to check through all release tags",
+            "$url = 'https://api.github.com/repos/pester/Pester/releases'",
+            "$latest_ver = [Version]::new(0,0,0,0) # note: Powershell 5 does not support casting 'int' or 'float' to 'System.Version'",
+            "$releases = $(Invoke-WebRequest $url).Content | ConvertFrom-Json",
+            "$releases | ForEach-Object {",
+            "    if (!($_.tag_name -match '([\\d.]+)')) { return }",
+            "    $ver = [Version]::new($matches[1])",
+            "    if ($ver -gt $latest_ver) { $latest_ver = $ver }",
+            "}",
+            "if ($latest_ver -eq [Version]::new(0,0,0,0)) { error \"Could not match version string in '$url'\"; break }",
+            "Write-Output $latest_ver"
+        ],
+        "regex": "([\\d.]+)"
     },
     "autoupdate": {
         "url": "https://globalcdn.nuget.org/packages/pester.$version.nupkg"