docs: Improve "data dictionary" section

[scarmuega]

The data dictionary section of the documentation should provide more detail about each event.

Ideally, we should have a title for each event with the following content:

• A short description of what it represents (one-liner)
• A short description of how it is obtained from the block data (1 or 2 paragraphs)
• A table with a row for each field of the payload (columns for name, data type and description)

[ch1n3du]

I wanted to clarify what you meant by the description of how the events are obtained from the block data. And on the third point I wanted to ask if the table should include the fields of the EventContext struct that are part of the current documentation, as the page seems to focus on the EventData enum

[scarmuega]

very nice job, great 1st issue!