Site: HTTP to HTTPS redirection is not working

Restore .htaccess file which was removed accidentally by commit
c1bf421c0816909fe53d557eb5ee012f779bfa11 after introducing an explicit
`include` directive. Add the .htaccess file in the `include` directive
to ensure that it is not lost when generating the website.
diff --git a/site/_config.yml b/site/_config.yml
index bddd5aa..b6662cd 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -21,7 +21,7 @@
 repository: https://github.com/apache/calcite
 destination: target
 exclude: [README.md,Gemfile*]
-include: [".asf.yaml"]
+include: [".htaccess", ".asf.yaml"]
 keep_files: [".git", ".svn", "javadocAggregate", "avatica", "docs/cassandra.html"]
 
 collections: