PR tutorial update

[wpotrzebowski]

P(R) tutorial updated to version 6. It seems that SasView 6 works better/has better defaults than SasView 5 and therefore it maybe not as a educational as previous version but it still demonstrates purpose.

It also has a GitHub action that auto-generates PDFs files from the new/modified fodt files.

Resolves #16 #20

[smk78]

This PR does 3 things:

• it provides an updated P(r) Tutorial revised for the changes to this perspective as featured in SasView 6.x;
• it introduces CI infrastructure to dynamically build Tutorial pdf's from associated .fodt files, a long-standing wish!
• and it updates the instructions in the repo README file.

I am not competent to review the CI scripts but can see the intent and figure @wpotrzebowski has tested them!

The changes to the README look good to me.

As regards the Tutorial itself:

• it looks like a page break has been lost immediately before Preamble;
• does the Preamble in fact want to be replaced with the new wording in the 6.2.0 installer licence?
• the copyright text needs reinstating;
• comparing p9 & p10, it looks as if the first figure on p10 could be moved up slightly which ought then to allow for a blank line to be inserted on p11 after the paragraph ending 'be considered with some care'.

I think this PR also addresses the following issues:
#20
#19
#16

Good work!