add(zmd): parse markdown file contents and display the parsed contents

Not everything can be parsed and displayed correctly yet, however this
will the default file format to use for adding page contents (i.e.
normal pages, blog entries, etc.)

build.zig

@@ -25,6 +25,10 @@ pub fn build(b: *std.Build) void {
         .target = target,
         .timestamp = true,
     });
+    const zmd_dep = b.dependency("zmd", .{
+        .optimize = optimize,
+        .target = target,
+    });
 
     const exe = b.addExecutable(.{
         .name = "tui-website",
@@ -34,6 +38,7 @@ pub fn build(b: *std.Build) void {
     });
     exe.root_module.addImport("vaxis", vaxis_dep.module("vaxis"));
     exe.root_module.addImport("zlog", zlog_dep.module("zlog"));
+    exe.root_module.addImport("zmd", zmd_dep.module("zmd"));
 
     // This declares intent for the executable to be installed into the
     // standard location when the user invokes the "install" step (the default