memberships: modal for errors (#133)

* unpolished version of error modal rendering

* rework of html files. template implemented

* new html files

* minor fixes.

* minor fixes

* title changes
diff --git a/core/auth/memberships/.gitignore b/core/auth/memberships/.gitignore
index 6ce208d..fd1862e 100644
--- a/core/auth/memberships/.gitignore
+++ b/core/auth/memberships/.gitignore
@@ -1,2 +1,3 @@
 *.db
 memberships*
+!memberships-tmpl/
\ No newline at end of file