Upgrade hextra theme v0.5.1 → v0.8.4 for Hugo v0.144 compatibility

.Site.GoogleAnalytics was removed in recent Hugo versions, causing
build failures with the old theme version.

Author: chraibi

go.mod

@@ -2,4 +2,4 @@ module github.com/PedestrianDynamics/PedestrianDynamics.github.io
 
 go 1.21
 
-require github.com/imfing/hextra v0.5.1 // indirect
+require github.com/imfing/hextra v0.8.4 // indirect

go.sum

@@ -1,2 +1,8 @@
 github.com/imfing/hextra v0.5.1 h1:/IUv+wfYUjxwj3VolVgDFYY0NjuuRP3Hlx6B8ckOAYg=
 github.com/imfing/hextra v0.5.1/go.mod h1:cEfel3lU/bSx7lTE/+uuR4GJaphyOyiwNR3PTqFTXpI=
+github.com/imfing/hextra v0.8.4 h1:cR4asr0TeDlqHPHLdTpMQJOjVeXnq8nfLMzcF0pld+w=
+github.com/imfing/hextra v0.8.4/go.mod h1:cEfel3lU/bSx7lTE/+uuR4GJaphyOyiwNR3PTqFTXpI=
+github.com/imfing/hextra v0.9.0 h1:1UyLZgS1eayce2ETCOjAQssXpkRz3HDrIs/fljH0lkU=
+github.com/imfing/hextra v0.9.0/go.mod h1:cEfel3lU/bSx7lTE/+uuR4GJaphyOyiwNR3PTqFTXpI=
+github.com/imfing/hextra v0.12.1 h1:3t1n0bmJbDzSTVfht93UDcfF1BXMRjeFojA071ri2l8=
+github.com/imfing/hextra v0.12.1/go.mod h1:vi+yhpq8YPp/aghvJlNKVnJKcPJ/VyAEcfC1BSV9ARo=