Polish the "Using Abseil in WebRTC" docs

Move the "How to depend on Abseil" section higher up to make it more
visible, and fix a few language nits.

Bug: none
Change-Id: I17096edbb2d55291f5ad512b345cf24c979f73f0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/188625
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32422}

abseil-in-webrtc.md

diff --git a/abseil-in-webrtc.md b/abseil-in-webrtc.md
index da03af0..79b1031 100644
--- a/abseil-in-webrtc.md
+++ b/abseil-in-webrtc.md
@@ -9,6 +9,17 @@
 
 [abseil]: https://abseil.io/about/
 
+
+## How to depend on Abseil
+
+For build targets of type `rtc_library`, `rtc_source_set` and
+`rtc_static_library`, dependencies on Abseil need to be listed in `absl_deps`
+instead of `deps`.
+
+This is needed in order to support the Abseil component build in Chromium. In
+that build mode, WebRTC will depend on a monolithic Abseil build target that
+will generate a shared library.
+
 ## **Allowed**
 
 * `absl::InlinedVector`
@@ -63,12 +74,3 @@
 These are optimized for speed, not binary size. Even `StrCat` calls
 with a modest number of arguments can easily add several hundred bytes
 to the binary.
-
-## How to depend on Abseil
-
-For build targets `rtc_library`, `rtc_source_set` and `rtc_static_library`,
-dependencies on Abseil need to be listed in `absl_deps` instead of `deps`.
-
-This is needed in order to support the Abseil component build in Chromium. In
-such build mode, WebRTC will depend on a unique Abseil build target what will
-generate a shared library.