Add Terraform files to default exclude filters

.terraform directory is automatically generated by Terraform. It contains downloaded providers and modules, none of which are useful to search for (it's comparable to node_modules but for Terraform).

There are also tfstate files that are stored outside of .terraform directory which contain Terraform state which again, aren't particularly useful to search for - they are JSONs, but not designed to be user-readable, you can think of them as SQL files. The wildcard is necessary because Terraform likes adding random extra extensions to filenames like .backup (terraform.tfstate.42.backup, where 42 is an integer representing backup number) or .lock.info (.terraform.tfstate.lock.info), and it's possible that future versions will add new possible additional extensions.