Update bidder creation(java) doc with alias feature

prebid-server/developers/add-new-bidder-java.md

@@ -84,7 +84,7 @@ adapters:
  pbs-enforces-ccpa: true
  modifying-vast-xml-allowed: true
  deprecated-names:
- aliases:
+ aliases: {}
  meta-info:
  maintainer-email: maintainer@email.com
  app-media-types:
@@ -124,6 +124,63 @@ The url of your user syncer can make use of the following privacy policy macros
 
 - Change the `usersync:type` value to `redirect` or `iframe` specific to your bidder.
 
+### Create bidder alias
+If you want to add bidder that is an alias of existing bidder, you need just to update configuration of parent bidder:
+
+Example of adding bidder alias:
+```yaml
+adapters:
+ {bidder}:
+ enabled: false
+ endpoint: http://possible.endpoint
+ pbs-enforces-gdpr: true
+ pbs-enforces-ccpa: true
+ modifying-vast-xml-allowed: true
+ deprecated-names:
+ aliases: 
+ {bidderAlias}:
+ endpoint: http://possible.alias/endpoint
+ app-media-types:
+ - banner
+ - video
+ site-media-types:
+ - banner
+ - video
+ usersync:
+ cookie-family-name: {bidderAlias}
+ meta-info:
+ maintainer-email: maintainer@email.com
+ app-media-types:
+ - banner
+ - video
+ - audio
+ - native
+ site-media-types:
+ - banner
+ - video
+ - audio
+ - native
+ supported-vendors:
+ vendor-id: your_vendor_id
+ usersync:
+ url: your_bid_adapter_usersync_url
+ redirect-url: /setuid?bidder={bidder}&gdpr={%raw%}{{gdpr}}{%endraw%}&gdpr_consent={%raw%}{{gdpr_consent}}{%endraw%}&us_privacy={%raw%}{{us_privacy}}{%endraw%}
+ cookie-family-name: {bidder}
+ type: redirect
+ support-cors: false
+```
+
+Aliases are configured by adding child configuration object at `adapters.{bidder}.aliases.{bidderAlias}`
+
+Aliases support the same configuration options that their bidder counterparts support except `aliases` (i.e. it's not possible
+to declare alias of an alias). 
+
+{: .alert.alert-warning :}
+**Aliases cannot declare support for media types not supported by their parent bidders**<br />
+However aliases could narrow down media types they support.<br />
+For example: if the bidder is written to not support native site requests, then an alias cannot magically decide to change that;
+However, if a bidder supports native site requests, and the alias does not want to for some reason, it has the ability to remove that support.
+
 ### Bidder Parameters
 
 Your bid adapter might require extra information from the publisher to form a request to your bidding server. The bidder parameters JSON Schema codifies this information to allow Prebid Server to verify requests and to provide an API for third party configuration systems.