Add cli documentation for COMPOSER_HTACCESS_PROTECT env variable

doc/03-cli.md

@@ -898,4 +898,8 @@ If set to 1, this env changes the default path repository strategy to `mirror` i
 of `symlink`. As it is the default strategy being set it can still be overwritten by
 repository options.
 
+### COMPOSER_HTACCESS_PROTECT
+
+Defaults to `true`. If set to `false`, Composer will not create `.htaccess` files in the composer home, cache, and data directories.
+
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