Python 3.10 compatibility changes

[isidentical]

• Add support for CI to test on 3.10
• Explicitly set the accessor. Before 3.9 the _accessor was not modified but with 3.10+ Path now modifies the _accessor. So we have to explicitly override it.
• Add follow_symlinks argument to the stat() (and raise a NotImplementError if it is falsy)

Fixes #94.

[isidentical]

and also in python 3.10 I see a new parameter in the write_text method. we need to add newline parameter to write_text method (and in the docs...)

I don't think S3Path explicitly defines this, but rather it is inherited so it is already covered (if I am not missing anything).

[liormizr]

Looks great I'll create a new version and update on the issue #94