[API] Add support for Windows arm64 for 6.1 and main branch (#949)

Author: kkebo

api/v1/install/dev/6.1/windows10.json

@@ -1,4 +1,6 @@
 ---
 layout: none
 ---
-{ "x86_64": {{ site.data.builds.swift-6_1-branch.windows10 | jsonify }}}
+{ "x86_64": {{ site.data.builds.swift-6_1-branch.windows10 | jsonify }},
+  "arm64": {{ site.data.builds.swift-6_1-branch.windows10-arm64 | jsonify }}
+}

api/v1/install/dev/main/windows10.json

@@ -1,4 +1,6 @@
 ---
 layout: none
 ---
-{ "x86_64": {{ site.data.builds.development.windows10 | jsonify }}}
+{ "x86_64": {{ site.data.builds.development.windows10 | jsonify }},
+  "arm64": {{ site.data.builds.development.windows10-arm64 | jsonify }}
+}