docs: add notice for uint conversion before 0.8.0
docs: edit sentence structure + remove 'result in `address payable`'
docs: add keyword 'explicitly' to be more specific for `address payable`
docs: edit notice uint to address conversion change since 0.8.0
Co-authored-by: Kamil Śliwak <cameel2@gmail.com>
Enhancing all the .rst doc files by adding highlighting for the code snippets, including the following langs:
1. Solidity
2. bash
3. javascript
4. assembly
The topic of converting a smaller type into a larger one is orthogonal to the one discussed in the example (namely, conversion between signed and unsigned integers).
Therefore, we change the `int8` to an `int` to make the example clearer.
