Change: add vcpkg.json to instruct vcpkg what dependencies we require

This works on all OSes, making it far simpler for any developer
to jump in. Just install vcpkg, run "vcpkg install" in our root,
and you have all the dependencies.

vcpkg.json

@@ -0,0 +1,54 @@
+{
+  "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg.schema.json",
+  "dependencies": [
+    {
+      "name": "breakpad",
+      "platform": "!(windows & arm)"
+    },
+    {
+      "name": "curl",
+      "platform": "linux",
+      "features": [
+        "http2"
+      ]
+    },
+    {
+      "name": "dbus",
+      "platform": "linux",
+      "default-features": false
+    },
+    {
+      "name": "fontconfig",
+      "platform": "linux"
+    },
+    {
+      "name": "freetype",
+      "platform": "linux"
+    },
+    {
+      "name": "harfbuzz",
+      "platform": "linux"
+    },
+    {
+      "name": "icu",
+      "platform": "linux"
+    },
+    {
+      "name": "liblzma"
+    },
+    {
+      "name": "libpng"
+    },
+    {
+      "name": "lzo"
+    },
+    {
+      "name": "sdl2",
+      "platform": "linux"
+    },
+    {
+      "name": "zlib"
+    }
+  ],
+  "builtin-baseline": "94cf042e6b7713913a3b3150f3ca3d0f4550f7c4"
+}