add FAQ to explorer footer (MystenLabs#12299)

## Description 

Describe the changes or additions included in this PR.
Add FAQ to explorer footer.
<img width="383" alt="Screenshot 2023-06-01 at 4 41 51 PM"
src="https://github.com/MystenLabs/sui/assets/126525197/a49d03a6-0974-4559-9d96-2ab59b4d9ae9">
<img width="593" alt="Screenshot 2023-06-01 at 4 41 32 PM"
src="https://github.com/MystenLabs/sui/assets/126525197/fc2b621f-b169-44dd-971f-8577dc525fc4">



## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [x] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

apps/explorer/src/components/footer/Footer.tsx

@@ -11,7 +11,7 @@ import { Text } from '~/ui/Text';
 function FooterLinks() {
     return (
         <div className="flex flex-col items-center justify-center gap-6 md:flex-row md:justify-end">
-            <ul className="flex gap-6 md:flex-row">
+            <ul className="flex gap-4 md:flex-row md:gap-6">
                 {footerLinks.map(({ title, href }) => (
                     <li key={href}>
                         <Link variant="text" href={href}>

apps/explorer/src/components/footer/footerLinks.tsx

@@ -21,6 +21,7 @@ function FooterIcon({ children }: { children: ReactNode }) {
 }
 
 export const footerLinks = [
+    { title: 'FAQ', href: 'https://docs.mystenlabs.com/explorer/faq' },
     { title: 'Blog', href: 'https://medium.com/mysten-labs' },
     {
         title: 'Whitepaper',