feat: embed web assets

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

web/web.go

+package web
+
+import (
+	"embed"
+	"io/fs"
+)
+
+//go:embed static/* templates/* themes/*
+var files embed.FS
+
+// FS returns a filesystem with the default web assets.
+func FS() fs.FS {
+	return files
+}