Upgrade eslint-plugin-matrix-org to 1.2.1

This upgrade came with a number of new lints that needed to be fixed across the code base. Primarily: explicit return types on functions, and explicit visibility modifiers on class members.

src/button/CopyButton.tsx

@@ -16,6 +16,7 @@ limitations under the License.
 
 import { useTranslation } from "react-i18next";
 import useClipboard from "react-use-clipboard";
+import { FC } from "react";
 
 import { ReactComponent as CheckIcon } from "../icons/Check.svg";
 import { ReactComponent as CopyIcon } from "../icons/Copy.svg";
@@ -28,14 +29,15 @@ interface Props {
   variant?: ButtonVariant;
   copiedMessage?: string;
 }
-export function CopyButton({
+
+export const CopyButton: FC<Props> = ({
   value,
   children,
   className,
   variant,
   copiedMessage,
   ...rest
-}: Props) {
+}) => {
   const { t } = useTranslation();
   const [isCopied, setCopied] = useClipboard(value, { successDuration: 3000 });
 
@@ -62,4 +64,4 @@ export function CopyButton({
       )}
     </Button>
   );
-}
+};