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**

检查用于加载反馈的 doPost() 函数、模组下载优先级逻辑以及“打开下载文件夹”等新按钮的 UI 组件。检查模组大小的计算和显示方式，并检查索引页上的图像渲染。需要检查输出日志保存机制，以避免包含残留文件。

由索引模型根据 Issue 内容生成。