Documentation/cli: Add the configuration and command history file

Close #1714.

Documentation/cli/README.md

+# Configuration
+
+Delve can be configured via the configuration file located in `$HOME/.config/dlv/config.yml`.
+You can open the file and discover all the configurable options and their default value.
+
+# History
+
+The command history of delve debugger is stored in `$HOME/.config/dlv/.dbg_history`.
+
 # Commands
 
 Command | Description

pkg/terminal/docgen.go

@@ -27,6 +27,13 @@ func replaceDocPath(s string) string {
 }
 
 func (commands *Commands) WriteMarkdown(w io.Writer) {
+	fmt.Fprint(w, "# Configuration\n\n")
+	fmt.Fprint(w, "Delve can be configured via the configuration file located in `$HOME/.config/dlv/config.yml`.\n")
+	fmt.Fprint(w, "You can open the file and discover all the configurable options and their default value.\n\n")
+
+	fmt.Fprint(w, "# History\n\n")
+	fmt.Fprint(w, "The command history of delve debugger is stored in `$HOME/.config/dlv/.dbg_history`.\n\n")
+
 	fmt.Fprint(w, "# Commands\n\n")
 
 	fmt.Fprint(w, "Command | Description\n")