[Minor Update] Easier road construction and Flatten operation.

Greetings! The main contents of the update include: [h3]New Operation[/h3] [list] [*] Roads can be built automatically from head to tail, no need to click one by one. [*] The Flatten operation can be set to "fill only" or "extract only" by clicking the "..." button above. [/list] [h3]Game Improvement[/h3] [list] [*] The work unit no longer overrides its own charging task when there is dual highest priority. [*] Fixed an issue that may cause the game to freeze in some cases. [/list] Thanks for your support, Wish you good game and have fun~