Python 3.9, pandas 2.2 and another change of URL

What's Changed

• @jm-rivera fixed a new URL break (#35, #36)
• minimal Python version is 3.9
• updated pandas (to version 2.2) and other dependecies
• considering getting data through SDMX endpoint in #39

Oct 2021 URL fixed

0.7.0

add link to Actions

New source URL structure and encodings

@aneziac updated links to IMF website and checked files encodings

dates() and all_dates() show downloadable WEO releases

0.4.0

pin up version