feat: smart tx optional prority fee

[sarmatdev]

Resolves #81

[0xIchigo]

gm and thank you for your contribution! There seems to be a bit of a mix-up with resolving #81 — this isn't just about using a user-provided priority fee, as that defeats the purpose of fetching and using the most optimal priority fee. Instead, the user should provide an upper limit to cap what the priority fee used is. This way, users can limit the priority fee to a certain range instead of what is being returned by the Priority Fee API

Consider the following scenarios where we cap priority fees at 10k:

• If the priority fee estimate based on the serialized transaction is 5k, then we'd use 5k
• If the priority fee estimate based on the serialized transaction is 10k, then we'd use 10k
• If the priority fee estimate based on the serialized transaction is 15k, then we'd use 10k

The idea here is to cap the priority fees at some number and take the minimum of the user-provided cap and the estimate returned by the Priority Fee API

[sarmatdev]

gm ser, delivered the fix