Add --experimental-string-processing to future changes

CHANGES.md

@@ -23,6 +23,7 @@
 
 ### Documentation
 
+- `--experimental-string-processing` will be enabled by default in the future (#2273)
 - Fix typos discovered by codespell (#2228)
 - Fix Vim plugin installation instructions. (#2235)
 - Add new Frequently Asked Questions page (#2247)

docs/the_black_code_style/current_style.md

@@ -250,6 +250,8 @@ If you are adopting _Black_ in a large project with pre-existing string conventi
 you can pass `--skip-string-normalization` on the command line. This is meant as an
 adoption helper, avoid using this for new projects.
 
+(labels/experimental-string)=
+
 As an experimental option (can be enabled by `--experimental-string-processing`),
 _Black_ splits long strings (using parentheses where appropriate) and merges short ones.
 When split, parts of f-strings that don't need formatting are converted to plain

docs/the_black_code_style/future_style.md

@@ -33,3 +33,10 @@ with \
 
 Although when the target version is Python 3.9 or higher, _Black_ will use parentheses
 instead since they're allowed in Python 3.9 and higher.
+
+## Improved string processing
+
+Currently, _Black_ does not split long strings to fit the line length limit. Currently,
+there is [an experimental option](labels/experimental-string) to enable splitting
+strings. We plan to enable this option by default once it is fully stable. This is
+tracked in [this issue](https://github.com/psf/black/issues/2188).