feat(post form): replace single return with double return on submit, because markdown is mandatory on plebbit, but a user from 4chan won't know that

src/components/post-form/post-form.tsx

@@ -183,7 +183,8 @@ const PostFormTable = ({ closeForm }: { closeForm: () => void }) => {
               wrap='soft'
               ref={textRef}
               onChange={(e) => {
-                isInPostPage ? setContent.content(e.target.value) : setSubmitStore({ content: e.target.value });
+                const content = e.target.value.replace(/\n/g, '\n\n');
+                isInPostPage ? setContent.content(content) : setSubmitStore({ content });
               }}
             />
           </td>

src/components/reply-modal/reply-modal.tsx

@@ -95,7 +95,10 @@ const ReplyModal = ({ closeModal, parentCid, scrollY }: ReplyModalProps) => {
             wrap='soft'
             ref={textRef}
             placeholder={_.capitalize(t('comment'))}
-            onChange={(e) => setContent.content(e.target.value)}
+            onChange={(e) => {
+              const content = e.target.value.replace(/\n/g, '\n\n');
+              setContent.content(content);
+            }}
             autoFocus={!isMobile} // autofocus causes auto scroll to top on mobile
           />
         </div>