fix spelling mistake and properly set install to PHONY target

Makefile

@@ -1,7 +1,7 @@
 INSTALL_DIR=~/.local/bin
 
 all:
-	@echo "Pleas run 'make install'"
+	@echo "Please run 'make install'"
 
 install:
 	@echo ""
@@ -17,3 +17,5 @@ install:
 	@echo 'p <bookmark_name> - Prints the directory associated with "bookmark_name"'
 	@echo 'd <bookmark_name> - Deletes the bookmark'
 	@echo 'l                 - Lists all available bookmarks'
+
+.PHONY: all install