lib,shared: Update README's based on contents of these dirs.

dpgeorge · dpgeorge · commit e3291e1801f2 · 2021-07-13T00:17:02.000+10:00
Signed-off-by: Damien George &lt;damien@micropython.org&gt;
diff --git a/lib/README.md b/lib/README.md
@@ -1,2 +1,3 @@
-This directory contains standard, low-level C libraries with emphasis on
-being independent and efficient.  They can be used by any port.
+This directory contains third-party, low-level C libraries and SDKs.
+Libraries that do not target any specific platform are generally chosen
+based on them being independent and efficient.
diff --git a/shared/README.md b/shared/README.md
@@ -0,0 +1,3 @@
+This directory contains libraries, utilities and helper code developed
+specifically for this project.  The code is intended to be portable and
+usable by any port.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+This directory contains libraries, utilities and helper code developed`
	`2`	`+specifically for this project. The code is intended to be portable and`
	`3`	`+usable by any port.`