Add Translations layer (#2288)

* Add rough translations support into CTFd
* Add `flask-babel` dependency
* Adds language column to users table
* Closes #570 

---------

Co-authored-by: Miłosz Skaza <milosz.skaza@ctfd.io>

migrations/versions/0def790057c1_add_language_column_to_users_table.py

@@ -0,0 +1,23 @@
+"""Add language column to Users table
+
+Revision ID: 0def790057c1
+Revises: 46a278193a94
+Create Date: 2023-04-19 00:56:54.592584
+
+"""
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "0def790057c1"
+down_revision = "46a278193a94"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column("users", sa.Column("language", sa.String(length=32), nullable=True))
+
+
+def downgrade():
+    op.drop_column("users", "language")