Ui features (#6)

* fix #3: added h ui command to toggle ui
* fix #4: added -N flag to disable colors
* fixed styling of line numbers (-n)
* fix #5 add usage section
* add pkg/epub module readme
* add license terms to all file headers
* fixed usage printing
* added basic unit tests
* run the tests only on linux due to the use of base64 utitlity

cmd/root.go

@@ -1,3 +1,19 @@
+/*
+Copyright © 2025 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
 package cmd
 
 import (
@@ -27,6 +43,15 @@ func Execute(output io.Writer) int {
 		return 0
 	}
 
+	if conf.ShowHelp {
+		_, err := fmt.Fprintln(output, Usage)
+		if err != nil {
+			return Die(fmt.Errorf("failed to print to output: %s", err))
+		}
+
+		return 0
+	}
+
 	if conf.StoreProgress {
 		progress, err := GetProgress(conf)
 		if err == nil {