This patch implements the `CappedString::push` and `CappedString::push_truncating` methods, which are like `CappedString::push_str` and friends but take a single character rather than a string slice.
This patch implements the `CappedString::push` and `CappedString::push_truncating` methods, which are like `CappedString::push_str` and friends but take a single character rather than a string slice.