[feature] Set/show instance language(s); show post language on frontend (#2362)

* update go text, include text/display

* [feature] Set instance langs, show post lang on frontend

* go fmt

* WebGet

* set language for whole article, don't use FA icon

* mention instance languages + other optional config vars

* little tweak

* put languages in config properly

* warn log language parse

* change some naming around

* tidy up validate a bit

* lint

* rename LanguageTmpl in template

testrig/config.go

@@ -23,6 +23,7 @@ import (
 	"codeberg.org/gruf/go-bytesize"
 	"github.com/coreos/go-oidc/v3/oidc"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 )
 
 // InitTestConfig initializes viper configuration with test defaults.
@@ -68,6 +69,14 @@ var testDefaults = config.Configuration{
 	InstanceExposeSuspended:        true,
 	InstanceExposeSuspendedWeb:     true,
 	InstanceDeliverToSharedInboxes: true,
+	InstanceLanguages: language.Languages{
+		{
+			TagStr: "nl",
+		},
+		{
+			TagStr: "en-gb",
+		},
+	},
 
 	AccountsRegistrationOpen: true,
 	AccountsApprovalRequired: true,