Add Motivation & Background paragraph

[acka47]

Todo from the last meetings, see e.g. https://etherpad.lobid.org/p/reconciliation-december-2025

[acka47]

Taking another look at it, I would rather restructure the first paragraph, e.g. something like this:

Due to the Web's decentralized nature, there is nothing preventing a service from publishing a new URI for an entity or concept which is already expressed elsewhere. As a result, for many entities you will find multiple IDs with different descriptions all over the web. One promise of Linked Open Data is the ability to mix up the data from different publishers. To be able to do this for a specific entity, one needs to first identify IDs and description denoting the same entity across services. This process of singling out and eventually integrating data from sources which do not share common unique identifiers often requires matching (or reconciling, merging) records which refer to the same entities.

I will just commit this.