[pv] Improvement Suggestions

Content

• Give a more detailed link between the pv and the topics listed in the overview. Email Tom for references for each topic (@jstac);
• Integrate "In asset pricing theory, and in economic dynamics more generally, a basic topic is the relationship among different time series." into the the list above;
• Give a concrete example for the setup in the analysis part (i.e., a real-world example for each parameter)
• Add a link for "difference equation"
• Explain that we are calculating the bubble component before we start our calculation (giving more context before calculations.
• Do a spell check and fix ``