fix: set width to 860px to optimize reading experience

src/common/constants.ts

@@ -1,6 +1,6 @@
 export const SIDEBAR_WIDTH = 208;
 export const TOC_WIDTH = 208;
-export const CONTENT_MAX_WIDTH = 1175;
+export const CONTENT_MAX_WIDTH = 860;
 
 export const SHIKI_THEME = 'Material-Theme-Default';
 export const THEME_STORAGE_KEY = 'theme';