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

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

Author: claude

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

@@ -63,8 +63,10 @@
     "prob",
     "chi",
     "squared",
+    "chisq",
     "chisquare",
     "chisquared",
+    "chi-square",
     "chi-squared",
     "cdf",
     "pdf",