feat: add decimals to internal assets

[SirTLB]

This pull requests add a decimal field to the internal asset states, this simplifies translations to a chains requested decimal amounts.

• [x] I have read Migaloo's contribution guidelines.
• [x] My pull request has a sound title and description (not something vague like Update index.md)
• [x] All existing and new tests are passing (if any).
• [x] I updated/added relevant documentation.
• [x] The code is formatted properly using eslint

[nick134-bit]

LGTM