fix: override for c8 to use yargs@^18 for Node 26

To work around a crash on Node 25/26
(<nodejs/node#62083>) caused by an extensionless
`./yargs` file in yargs@17 (<nodejs/node#62083>)
which started being interpreted as `type: "module"` in Node.js 25.7 due
to <nodejs/node#61600>, which was reverted by
<nodejs/node#62083> for Node.js 25, but retained
for Node.js 26.

Work around the issue by overriding the c8 yargs dependency to use
yargs@^18.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

Author: kevinoid

package.json

@@ -64,6 +64,11 @@
     "nodecat": "^2.0.0",
     "rimraf": "^6.1.2"
   },
+  "overrides": {
+    "c8": {
+      "yargs": "^18.0.0"
+    }
+  },
   "engines": {
     "node": "20 || >=22",
     "npm": ">=1.3.7"