Add reference to config_dbms.http_enabled_modules. (#47)

Author: lidiazuin

modules/ROOT/pages/introduction.adoc

@@ -15,6 +15,9 @@ The default timeout is `60` seconds.
 Responses from the HTTP API can be transmitted as JSON streams, resulting in better performance and lower memory overhead on the server side.
 To use streaming, supply the header `X-Stream: true` with each request.
 
+In case `dbms.http_enabled_modules` is defined in `conf/neo4j.conf` and you want to use HTTP API, then the parameter must include `TRANSACTIONAL_ENDPOINTS`.
+See xref:4.4@operations-manual:ROOT:reference/configuration-settings/index.adoc#config_dbms.http_enabled_modules[Operations Manual -> Configuration settings `config_dbms.http_enabled_modules`] for more information.
+
 [NOTE]
 ====
 * Literal line breaks are not allowed inside Cypher statements.
@@ -29,4 +32,3 @@ In order to speed up queries in repeated scenarios, try not to use literals but
 This will let the server cache query plans.
 See xref:4.4@cypher-manual:ROOT:syntax/parameters/index.adoc#cypher-parameters[Cypher Manual -> Parameters] for more information.
 ====
-