Add link to obtain API key in README

Update API key link format in README

Update README.md

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Merge branch 'main' of https://github.com/tradingeconomics/notebooks

add the country package

update dataframe columns definition

updated dataframe construction

updated dataframe columns api calls

add x-axis and remove earliest date

convert date and merge df

updated dates as index for plotting

time acending n plot x y

update new functions

date columns and plotting fixed