chore: add fees documentation

[MakMuftic]

One of the PRs related to adding fee-handling documentation across all services.

Description

• Add basic structure of /docs folder
• Add partial Home page for fee oracle technical documentation
• Add fee estimate message technical documentation

Related Issue Or Context

Related to #106

How Has This Been Tested? Testing details.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation

Checklist:

• I have commented my code, particularly in hard-to-understand areas.
• I have ensured that all acceptance criteria (or expected behavior) from issue are met
• I have updated the documentation locally and in docs.
• I have added tests to cover my changes.
• I have ensured that all the checks are passing and green, I've signed the CLA bot