Update readme about deployment / build
Update readme about deployment / build

alphagov/transactions-explorer,alphagov/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,alphagov/transactions-explorer,alphagov/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,alphagov/transactions-explorer