Re-wrote from scratch in Golang

- Re-implemented the project in Golang, and deprecated Python entirely
- Implemented several new, long-requested features
- Refactored cheatsheets into a separate repository

internal/sheet/tagged.go

@@ -0,0 +1,15 @@
+package sheet
+
+// Tagged returns true if a sheet was tagged with `needle`
+func (s *Sheet) Tagged(needle string) bool {
+
+	// if any of the tags match `needle`, return `true`
+	for _, tag := range s.Tags {
+		if tag == needle {
+			return true
+		}
+	}
+
+	// otherwise, return `false`
+	return false
+}