docusaurus/v2/lib/theme/Docs/styles.css

.mainContainer {
  display: flex;
  flex-direction: row;
  margin-bottom: 30px;
  margin-left: auto;
  margin-right: auto;
  margin-top: 40px;
  justify-content: space-between;
}

.docContent {
  flex-grow: 1;
}