Add quirks setting to control DECSET/DECRST 12

Fixes #5314

typings/xterm.d.ts

@@ -197,6 +197,12 @@ declare module '@xterm/xterm' {
      */
     minimumContrastRatio?: number;
 
+    /**
+     * Control various quirks features that are either non-standard or standard
+     * in but generally rejected in modern terminals.
+     */
+    quirks?: ITerminalQuirks;
+
     /**
      * Whether to reflow the line containing the cursor when the terminal is
      * resized. Defaults to false, because shells usually handle this
@@ -406,6 +412,21 @@ declare module '@xterm/xterm' {
     extendedAnsi?: string[];
   }
 
+  /**
+   * Control various quirks features that are either non-standard or standard
+   * in but generally rejected in modern terminals.
+   */
+  export interface ITerminalQuirks {
+    /**
+     * Enables support for DECSET 12 and DECRST 12 which controls cursor blink.
+     * Programs such as `vim` may use this to set the cursor blink state but may
+     * not change it back when exiting. Generally the terminal emulator should
+     * be in control of whether the cursor blinks or not and the application in
+     * modern terminals. Note that DECRQM works regardless of this option.
+     */
+    allowSetCursorBlink?: boolean;
+  }
+
   /**
    * Pty information for Windows.
    */