Feature: tier XI compatibility

Prepares BlitzKit for tier XI tanks ahead of their release. Tier X was hardcoded as the maximum in the tank search filters, the guesser and the tech tree, and had no roman numeral beyond X.

- Added `XI` to `TIER_ROMAN_NUMERALS`
- Added an awaitable tier list derived from the highest tier in the tank definitions, so nothing changes until tier XI tanks exist
- Used it for the tank search tier filters and the guesser tier picker and defaults
- Made the tech tree check for successors instead of assuming tier X is the last tier

Fixes #302

packages/website/src/components/Tankopedia/TechTreeSection/components/Node.tsx

@@ -127,7 +127,7 @@ export function Node({ id, highlight, nextIds, skeleton }: NodeProps) {
               </Text>
             </Flex>
 
-            {averages && nextTanks && tank.tier !== 10 && (
+            {averages && nextTanks && nextTanks.length > 0 && (
               <Text color="gray" size="1" mt="2">
                 {skeleton && <Skeleton height="1em" width="4em" />}
                 {!skeleton &&

packages/website/src/components/Tankopedia/TechTreeSection/index.tsx

@@ -191,7 +191,7 @@ export function TechTreeSection({ skeleton }: MaybeSkeletonComponentProps) {
             );
           })}
 
-          {master.tier < 10 && (
+          {master.successors.length > 0 && (
             <>
               <Arrow />
               {master.successors!.map((id, index) => (