Add Technical Background section

with browser automation subsection listing the main alternatives
Add explanation for what Selenium WebDriver is
Add Selenium reference
Make interview summary into a separate section
Remove outdated part of acknowledgement
Add Jack Franklin reference to motivate testing
Add reference to framework evaluation blog post
Use urldate instead of note in online references
Add transcript of interview with Marcus Ahnve
Add numbering of questions in interview with Johannes Edelstam
Add numbering of questions in interview with Patrik Stenmark
Add numbering of questions in interview with Marcus Ahnve
Add reference to specific interview question
Add single reference to multiple interview questions
Add some more references to interview questions
Use non-braking spaces in question references
Add some more references to interview questions

Also rephrase some sentences and split sections.
Motivate testing of private APIs, add reference
Fix typo in transcript
Understanding testing