README: Formatting

Bug: b/236395423
Change-Id: Ia1c7326c291d48f15e191fc9e2333f413682a579
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98600
Commit-Queue: Ted Pudlik <tpudlik@google.com>
Pigweed-Auto-Submit: Ted Pudlik <tpudlik@google.com>
Reviewed-by: Rob Mohr <mohrr@google.com>
diff --git a/README.md b/README.md
index 8548ab4..9d9e1fc 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 32-bit microcontrollers like the STMicroelectronics STM32L452 or the Nordic
 nRF52832.
 
-For more information please see our website: https://pigweed.dev/
+For more information please see our website: https://pigweed.dev/.
 
 ## Links