style(theme): fix selection style issue. (#546)

Author: jaywcjlove

themes/theme/src/index.tsx

@@ -95,9 +95,9 @@ export const createTheme = ({ theme, settings = {}, styles = [] }: CreateThemeOp
 
   if (settings.selection) {
     themeOptions[
-      '&.cm-focused .cm-selectionBackground, & .cm-selectionLayer .cm-selectionBackground, .cm-content ::selection'
+      '&.cm-focused .cm-selectionBackground, &.cm-focused .cm-line::selection, & .cm-selectionLayer .cm-selectionBackground, .cm-content ::selection'
     ] = {
-      backgroundColor: settings.selection,
+      backgroundColor: settings.selection + ' !important',
     };
   }
   if (settings.selectionMatch) {