如何将 CSS 代码添加到现有 CSS 文件中

<p>&quot;:root{{ --polaris-version-number:''3.21.1'; }}\nhtml, body{{ font-size:1.5rem; font-weight:400; line-height:2rem; text-transform:initial; letter-spacing:initial; font-weight:400; color:#212b36; }}\n@media (min-width: 40em){{ html, body{{ font-size:1.4rem; }} }}\nhtml, body, button{{ font-family:-apple-system, BlinkMacSystemFont, San Francisco, Roboto, Segoe UI, Helvetica Neue, sans-serif; }}\nhtml{{ position:relative; font-size:62.5%; -webkit-font-smoothing:antialiased; -moz-osx-font-smoothing:grayscale; -webkit-text-size-adjust:100%; -ms-text-size-adjust:100%; text-size-adjust:100%; text-rendering:optimizeLegibility; }}\nbody{{ min-height:100%; margin:0; padding:0; background-color:#f4f6f8; }}\n*, *::before, *::after{{ box-sizing:border-box; }}\nh1, h2, h3, h4, h5, h6, p{{ margin:0; font-size:1em; font-weight:400; }}\nbutton::-moz-focus-inner, [type='button']::-moz-focus-inner, [type='reset']::-moz-focus-inner, [type='submit']::-moz-focus-inner{{ border-style:none; }}\n@keyframes polaris-SkeletonShimmerAnimation{{ 0%{{ opacity:0.45; }} 100%{{ opacity:0.9; }} }}\n.Polaris-Avatar{{ position:relative; display:block; overflow:hidden; min-width:3.2rem; max-width:100%; background:#47c1bf; }}\n\n<style>\n.header {{ margin-top: 1px; border-bottom: 1px #c1c1c1 solid; padding: 5px; }}\n.header .logo {{ display: flex; align-items: center; justify-content: space-between; }}\n.header .logo .button-group {{ display: flex; align-items: center; }}\n.header .logo .button-group .button-item {{ margin-right: 10px; }}\n.header .logo .button-group .button-item:last-child {{ margin-right: 0; }}\n.dropdown-content {{ display: none; }}\n</style>\n</p>