Add documentation for command history feature

docs/diagrams/CommandHistorySequenceDiagram.puml

@@ -0,0 +1,49 @@
+@startuml
+!include style.puml
+skinparam ArrowFontStyle plain
+
+box UI UI_COLOR_T1
+participant ":CommandBox" as CommandBox UI_COLOR
+participant ":CommandExecutor" as CommandExecutor UI_COLOR
+end box
+
+box Logic LOGIC_COLOR_T1
+participant ":LogicManager" as LogicManager LOGIC_COLOR
+participant ":CommandHistory" as CommandHistory LOGIC_COLOR
+end box
+
+'box JavaFX JAVAFX_COLOR_T1
+participant ":TextField" as TextField JAVAFX_COLOR
+'end box
+
+-> CommandBox : handleKeyPressed(event)
+activate CommandBox
+
+CommandBox -> CommandExecutor : getPreviousCommandText()
+activate CommandExecutor
+
+CommandExecutor -> LogicManager : getPreviousCommandText()
+activate LogicManager
+
+LogicManager -> CommandHistory : getPrevious()
+activate CommandHistory
+
+CommandHistory --> LogicManager : commandText
+deactivate CommandHistory
+
+LogicManager --> CommandExecutor : commandText
+deactivate LogicManager
+
+CommandExecutor --> CommandBox : commandText
+deactivate CommandExecutor
+
+CommandBox -> TextField : setText(commandText)
+activate TextField
+
+TextField --> CommandBox
+deactivate TextField
+
+<-- CommandBox
+deactivate CommandBox
+
+@enduml