Add information about resource packs to the handbook

This should include the content of the following sections:

• https://wiki.eclipse.org/CBI#What.27s_provided.3F
• https://wiki.eclipse.org/CBI#Additional_Resource_Packs

Content can also be used from

• https://wiki.eclipse.org/Jenkins#About_resource_packs_and_quotas

More important than technical details (number of CPUs and RAM), is probably the process of how resource packs are assigned (https://wiki.eclipse.org/CBI#Assigning_Resource_Packs_to_a_Project) and how projects/orgs can check the status of resource pack allocation (https://wiki.eclipse.org/CBI#Sponsored_Projects).