[PATCH 1/2] README: Mention b4 and lei

[Kyle Meyer <kyle@kyleam.com>]

piem leans on b4 heavily, so it deserves a pointer in the README.
Plus, the next patch will mention b4 when it describes mailscripts,
and it seems a bit odd for that to be the only mention.

And lei wasn't a thing when this README was written, but it's
certainly worth highlighting now.
---
 README | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/README b/README
index a79f8eda..9c0bea47 100644
--- a/README
+++ b/README
@@ -5,9 +5,15 @@ piem --- Emacs tools and glue for working with public-inbox archives
 This project is currently in the early stages of development.  In
 general, anything that relates to interacting with public-inbox
 (https://public-inbox.org/README) archives from Emacs is worth
-considering, at least at this point.  Much of the current
-functionality focuses on mapping public-inbox endpoints (email, nntp,
-http, rss) to associated code repositories in order to apply patches.
+considering, at least at this point.
+
+Much of the current functionality focuses on mapping public-inbox
+endpoints (email, nntp, http, rss) to associated code repositories in
+order to apply patches, including integration with b4-am to extract
+and process patches (https://git.kernel.org/pub/scm/utils/b4/b4.git).
+Upcoming development will largely focus on extending the very basic
+support public-inbox's local email interface (lei).
+
 Documentation is available online at
 
     https://docs.kyleam.com/piem/
-- 
2.34.0