many many updates (check commit detail)

- updated dependencies
  - bumped react version 17 -> 18
- changed navbar button tag from `a` to `button`
- added locale info to url (made sure same url = same content)
- fixed 0 gettingconsidered as "unknown length" for
  word count in `PostCard`
- moved functions from `Page.tsx` to `helper.ts`
- added "translation not available" page

src/components/PostCard.tsx

@@ -78,7 +78,7 @@ const PostCard = (props: Props) => {
 
 	return (
 		<StyledPostCard>
-			<PostCardContainer to={process.env.PUBLIC_URL + postData.url}>
+			<PostCardContainer to={postData.url}>
 				<StyledTitle>
 					{postData.title || "No title"}
 					{/* show "(series)" for urls that matches regex "/series/<series-title>" */}
@@ -107,7 +107,7 @@ const PostCard = (props: Props) => {
 					&nbsp;&nbsp;&nbsp;&nbsp;
 					<FontAwesomeIcon icon={faBook} />
 					&nbsp;&nbsp;&nbsp;
-					{postData.wordCount
+					{typeof postData.wordCount === "number"
 						? postData.wordCount + " words"
 						: "unknown length"}
 				</StyledMetaContainer>