Refactor out the use of rice in favor of embed (#2)

Co-authored-by: James Mills <prologic@shortcircuit.net.au>
Reviewed-on: https://git.mills.io/prologic/spyda/pulls/2

internal/static/static.go

@@ -0,0 +1,36 @@
+package static
+
+import (
+	"embed"
+	"io/fs"
+	"log"
+	"net/http"
+)
+
+//go:embed css/*.css
+//go:embed img/*.png img/*.svg
+//go:embed js/*.js
+var files embed.FS
+
+// MustGetFile returns the contents of a file from static as bytes.
+func MustGetFile(name string) []byte {
+	b, err := files.ReadFile(name)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+// GetFilesystem returns a http.FileSystem for the static files.
+func GetFilesystem() http.FileSystem {
+	return http.FS(files)
+}
+
+// GetSubFilesystem returns a http.FileSystem for the static sub-files.
+func GetSubFilesystem(name string) http.FileSystem {
+	fsys, err := fs.Sub(files, name)
+	if err != nil {
+		log.Fatalf("error loading sub-filesystem for %q: %s", name, err)
+	}
+	return http.FS(fsys)
+}