docs: update conference talk submission docs

Fox Danger Piacentirequested to merge
fox/talk-submission-refinement into master

Description

This MR updates the existing documentation for the three-stage process for talk submission that worked very well this year.

Supplementary Information

Internal ticket: https://tasks.opencraft.com/browse/BB-10347

Testing instructions

View the rendered app and check that the links and display make sense.

Edited by Fox Danger Piacenti

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