[FEATURE]: Use JORAM data to retrieve gas prices

[carlosrsabreu]

Related issues

Closes #47

What does this PR do?

_{Clearly state the reason for this change. What problem is it solving or feature is it adding?}

Starts using JORAM gas prices and drop DRET gas prices, due to the reasons mentioned in the issue.

Solution Overview

_{Provide an overview of the solution implemented in this pull request. This should be a high level overview without getting into technical details. If applicable, include screenshots of UI or use GitHub compliant mermaid graphs to visually represent the solution.}

• Prices are now retrieved from the JORAM PDF;
• Extracted functions that should be global to a file called functions.py;

Implementation Details

_{Explain the details of the implementation and the reasoning behind it. Where should the reviewer start?}

• Reviewer should start in the file update_gas_prices.py.

[carlosrsabreu]

Made some last changes on the code, please @Dntfreitas or @HarryVasanth check and merge 👯

[Dntfreitas]

LGTM :)