Document file size Spring configuration for "deploy resources" endpoint

[nicpuppa]

To allow users to deploy resources via REST endpoint we added this 2 spring configuration properties in the application.properties file in /dist:

# Multipart file uploads
spring.servlet.multipart.max-file-size=4MB
spring.servlet.multipart.max-request-size=4MB

We did this because the default values of this properties are:

# Multipart file uploads
spring.servlet.multipart.max-file-size=1MB
spring.servlet.multipart.max-request-size=10MB

Since we have a property in Zeebe that configure the message size (maxMessageSize), this 2 properties should have the same value.

Users can leave the value of 4MB if they are using the default maxMessageSize or if they are using a lower value (the request will be rejected by the broker)
Users must increase those values if they are using an higher maxMessageSize, otherwise the request will be rejected by Spring itself