Add ISO 2533:1975/ADD 1:1985 calculations

[ronaldtse]

Table 1

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Table 2

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Table 3

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Table 4

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Table 5

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Table 6

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[newbthenewbd]

It seems that basically, this addendum just needs another round of tables generated (and perhaps a test if these derived formulae might be more accurate nonetheless), whereas the other, addendum-2, a conversion procedure from meters to feet? Not much, still took me a few reads :)

So gonna fetch them from https://github.com/metanorma/iso-2533 and adjust the generator soon, I guess that it's gonna go in the same pull request #31...

[newbthenewbd]

Hmm, looks like these addendum tables are not such nice yaml... Or are they supposed to look the way they do?

[ronaldtse]

@newbthenewbd indeed, we need to update how these tables are encoded...