[io.ascii.cds] Find "Explanations" position to identify continuation lines in Readme from column headings

[dhomeier]

Description

Follow-up to #15617 – this implements the approach described in #15617 (comment) to strip header lines just to the position before the start of the Explanations column, allowing the parser to automatically identify and merge continuation lines.

To be discussed if this

1. needs an extra test
2. should do a case-insensitive search for explanation

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[github-actions]

Hi humans 👋 - this pull request hasn't had any new commits for approximately 4 months. I plan to close this in 30 days if the pull request doesn't have any new commits by then.

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