Include documentation in the application

doc/keyboard-shortcuts.markdown

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+Keyboard shortcuts
+==================
+
+Board/Calendar/List view
+------------------------
+
+- Switch to the board view = **v b**
+- Switch to the calendar view = **v c**
+- Switch to the list view = **v l**
+
+Board view
+----------
+
+- New task = **n**
+- Expand/collapse tasks = **s**
+- Compact/wide view = **c**
+
+Application
+-----------
+
+- Open board switcher = **b**
+- Go to the search/filter box = **f**
+- Close dialog box = **ESC**
+- Submit a form = **CTRL+ENTER** or **⌘+ENTER**