Add delete key functionality .Fix Backspace line erase bug.

Co-authored-by: sigonasr2 <sigonasr2@gmail.com>

main.cpp

@@ -110,12 +110,22 @@ public:
 
 	void GetAnyKeyPress(olc::Key k)override{
 		lastBlinkTime=0.5f;
+		if (k==DEL){
+			if (cursors[0].pos==document[cursors[0].line].size()){
+				if (cursors[0].line<document.size()-1){
+					document[cursors[0].line].append(document[cursors[0].line+1]);
+					document.erase(document.begin()+cursors[0].line+1);
+				}
+			} else {
+				document[cursors[0].line].erase(cursors[0].pos,1);
+			}
+		} else
 		if (k==BACK){
 			if (cursors[0].pos==0){
 				if (cursors[0].line>0){
 					cursors[0].pos=document[cursors[0].line-1].size();
 					document[cursors[0].line-1].append(document[cursors[0].line]);
-					document[cursors[0].line--].clear();
+					document.erase(document.begin()+cursors[0].line--);
 				}
 			} else {
 				document[cursors[0].line].erase(cursors[0].pos---1,1);