Potential work-around for Rollup cyclic dependency bug (#2332)

# Motivation

There is a bug in Rollup that non-deterministically fails to detect
cyclic
dependencies. rollup/plugins#1425
As a result `lru-cache` is sometimes wrapped in a `requireLruCache`
function and sometimes it is not.
This makes our build non-deterministic.
`lru-caceh` is not itself part of a circular dependency but
`semver/classes/range.js`, which depends on `lru-cache`, is.
By depending on `lru-cache` directly from our app, we change the order
in which modules are analyzed by Rollup, hopefully avoiding the buggy
behavior.
It probably doesn't matter where we put this import, so I put it as
close to the root of the app as I could find.

# Changes

Add `import "lru-cache"` in frontend/src/routes/+layout.ts

# Tests

Inspected generated `vendor` chunk to see that it does not have
`hasRequiredLruCache`.
`dfx deploy nns-dapp` locally and did some manual testing.

frontend/src/routes/+layout.ts

@@ -1,3 +1,16 @@
+// There is a bug in Rollup that non-deterministically fails to detect cyclic
+// dependencies. https://github.com/rollup/plugins/issues/1425
+// As a result 'lru-cache' is sometimes wrapped in a require* function and
+// sometimes it is not. This makes our build non-deterministic.
+// lru-caceh is not itself part of a circular dependency but
+// semver/classes/range.js, which depends on lru-cache, is.
+// By depending on lru-cache directly from our app, we change the order in which
+// modules are analyzed, hopefully avoiding the buggy behavior.
+// It probably doesn't matter where we put this import, so I put it as close to
+// the root of the app as I could find.
+// TODO: Remove when the Rollup issue is fixed.
+import "lru-cache";
+
 export const prerender = true;
 
 // TODO: no ssr for local development until https://github.com/dfinity/ic-js/issues/238 solved