feat(cli): '--help' flag

this flag works the same way as calling fleck without any arguments, but omits the error at the end. A help page is somewhat standard, therefore i added this option / flag

cli/constants.go

@@ -30,6 +30,12 @@ func (a *Arguments) String() string {
 }
 
 var OPTIONS []Flag = []Flag{
+	{
+		"help",
+		false,
+		"prints the help page, exists",
+		"",
+	},
 	{
 		"debug",
 		false,

doc/Usage.md

@@ -20,6 +20,7 @@ Usage:
     fleck [Options] file
 
 Options:
+        --help                          prints the help page, exists
         --debug                         enables debug logs
         --version                       prints version and build information, exists
         --no-prefix                     hide the informational comments generated in the output html
@@ -41,6 +42,7 @@ exit status 1
 
 | Option                   | description                                                       | default value |
 | ------------------------ | ----------------------------------------------------------------- | ------------- |
+| `--help`                 | prints the help page, exists                                      | false         |
 | `--debug`                | enables debug logs                                                | false         |
 | `--version`              | prints version and build information, exists                      | false         |
 | `--no-prefix`            | hide the informational comments generated in the output html      | false         |

fleck.go

@@ -41,6 +41,10 @@ func main() {
 	if cli.GetFlag(cli.ARGUMENTS, "version") {
 		cli.PrintVersion(VERSION, BUILD_AT, BUILD_BY)
 	}
+	if cli.GetFlag(cli.ARGUMENTS, "help") {
+		cli.PrintShortHelp()
+		os.Exit(0)
+	}
 	if len(cli.ARGUMENTS.InputFile) == 0 {
 		cli.PrintShortHelp()
 		logger.LError("not enough arguments, specify an input file")