<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
  position: relative;
  text-align: center;
}
.cp_h1title:before,
.cp_h1title:after {
  position: absolute;
  content:'';
  width: 20px;/*カギ括弧の横幅*/
  height: 30px;/*カギ括弧の高さ*/
  border-style: solid;/*カギ括弧のスタイル*/
  border-color: #283593;/*カギ括弧の色*/
}
.cp_h1title:before {
  border-width: 2px 0 0 2px;
  top:0;
  left: 0;
}
.cp_h1title:after {
  border-width: 0 2px 2px 0;
  bottom:0;
  right: 0;
}