Trigger typing mode when ENTER is pressed

Splitting a block or inserting a new paragraph block by pressing ENTER
should engage typing mode.

blocks/editable/index.js

@@ -586,7 +586,6 @@ export default class Editable extends Component {
 				if ( event.shiftKey || ! this.props.onSplit ) {
 					this.editor.execCommand( 'InsertLineBreak', false, event );
 				} else {
-					event.stopImmediatePropagation();
 					this.splitContent();
 				}
 			}

editor/components/block-list/block.js

@@ -223,12 +223,9 @@ export class BlockListBlock extends Component {
 	}
 
 	maybeStartTyping() {
-		// We do not want to dispatch start typing if...
-		//  - State value already reflects that we're typing (dispatch noise)
-		//  - The current block is not selected (e.g. after a split occurs,
-		//    we'll still receive the keyDown event, but the focus has since
-		//    shifted to the newly created block)
-		if ( ! this.props.isTyping && this.props.isSelected ) {
+		// We do not want to dispatch start typing if state value already reflects
+		// that we're typing (dispatch noise)
+		if ( ! this.props.isTyping ) {
 			this.props.onStartTyping();
 		}
 	}
@@ -310,6 +307,9 @@ export class BlockListBlock extends Component {
 						createBlock( 'core/paragraph' ),
 					], this.props.order + 1 );
 				}
+
+				// Pressing enter should trigger typing mode after the content has split
+				this.maybeStartTyping();
 				break;
 
 			case UP: