A pretty straight copy of #861. Cutting down README.md example text since it seemed a little redundant with examples in the bullets.

-   For idiomatic Carbon code:
    -   `UpperCamelCase` will be used when the identifier can be resolved to a
        specific value at compile-time.
    -   `lower_snake_case` will be used when the identifier's value won't be
        known until runtime, such as for variables.
-   For Carbon-provided features:
    -   Keywords and type literals will use `lower_snake_case`.
    -   Other code will use the guidelines for idiomatic Carbon code.
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: josh11b <josh11b@users.noreply.github.com>

A pretty straight copy of #861. Cutting down README.md example text since it seemed a little redundant with examples in the bullets.

Primitive types have been renamed in pull request carbon-language#861 and also the design document.

Primitive types have been renamed in pull request carbon-language#861 and also the design document.

Primitive types have been renamed in pull request #861 and also the design document.

Primitive types have been renamed in pull request carbon-language#861 and also the design document.