General Minor Enhancements Part 3

Continuing from #65

- [ ] in the doPost() function, add better feedback when something is 'loading' (like a global loading symbol or loading bar which runs across the screen)
- [ ] Manually added mod option downloads are always added *after* the normal options. Therefore their priority levels can't be in-between the existing downloads, only can come after them. Not sure if this is the desired behavior, or if there is even a case where you would want this. But the behavior is confusing at the moment as in the JSON it's called "priority' for both priorities, even though they are different priorities.
- [ ] Add option to download only (stop after downloads complete)
- [ ] Add "open downloads folder" / "open installer folder" button
- [ ] Add free disk space check (Not implemented on mac, but otherwise DONE)
- [ ] Fix duplicate mod size (probably remove top mod size warning)
- [ ] On chrome, index page images look blurry due to chrome's resize algorithm (as compared to firefox). Consider pre-resizing the images to their native res or displaying them at their native res
- [ ] **Automatically saved output log at end of install includes `output.txt` which may be misleading as this is probably a leftover from the previous install, rather than from when the user ran the game**

檢查用於載入回饋的 doPost() 函式、模組下載優先順序邏輯以及「開啟下載資料夾」等新按鈕的 UI 元件。檢查模組大小的計算和顯示方式，並檢查索引頁上的圖像渲染。需要檢查輸出日誌儲存機制，以避免包含殘留檔案。

由索引模型根據 Issue 內容生成。