btest: Add version 7.15.1 (#13449)

* btest: Add version 7.15.1
* btest@7.15.1: Add newline
* btest@7.15.1: Fix formatting

---------

Co-authored-by: Aliaksandr Belik <1752374+aliesbelik@users.noreply.github.com>

bucket/btest.json

@@ -0,0 +1,22 @@
+{
+    "version": "7.15.1",
+    "description": "Mikrotik bandwidth test client and server for Windows",
+    "homepage": "https://mikrotik.com/",
+    "license": "Unknown",
+    "url": "https://download.mikrotik.com/routeros/7.15.1/btest.exe",
+    "hash": "22fc013945683da2ee41fbc84d1fbde88717ec419f81cd839a2bd50e69e839e7",
+    "bin": "btest.exe",
+    "shortcuts": [
+        [
+            "btest.exe",
+            "Mikrotik Bandwidth Test"
+        ]
+    ],
+    "checkver": {
+        "url": "https://mikrotik.com/download/",
+        "re": "([\\d\\.]+)\\ Stable"
+    },
+    "autoupdate": {
+        "url": "https://download.mikrotik.com/routeros/$version/btest.exe"
+    }
+}