style: align stats/base/dists/chisquare/median with namespace conventions

Added missing `chi-squared` (present in 13/14 siblings, 93%) and
`chisq` (11/14, 79%) to the keywords list. Both are standard
chi-squared-distribution aliases and complete the chi-* cluster
already present in the package.

Author: claude

lib/node_modules/@stdlib/stats/base/dists/chisquare/median/package.json

@@ -59,9 +59,11 @@
     "location",
     "percentile",
     "center",
+    "chisq",
     "chisquare",
-    "chi-square",
     "chisquared",
+    "chi-square",
+    "chi-squared",
     "univariate",
     "continuous"
   ]