fix: update eslint fixall setting in readme

What kind of change does this PR introduce? (check at least one)

[ ] Bugfix (non-breaking change which fixes an issue)
[ ] Feature (non-breaking change which adds functionality)
[ ] Code style update
[ ] Refactor (refactoring or adding test which isn't a fix or add a feature)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] Build-related changes
[x] Other, please describe: Readme update

Does this PR introduce a breaking change? (check one)

[ ] Yes
[x] No

Did you test your solution?

N/A

Problem Description

The current readme suggests using true as the value for "source.fixAll.eslint", which is deprecated. The value should be a string, of one of the following values: always, explicit, never. Explicit will only run this eslint save action when a save is explicitly made. See https://code.visualstudio.com/updates/v1_83#_code-actions-on-save-and-auto-save for more details.

Solution Description

Update readme to use the correct string value.

Side Effects, Risks, Impact

[ ] N/A

Aditional comments:

Experience-Monks / nextjs-boilerplate