doc: Fix case in titles

Unified case in titles.
Fixed small grammar issues.

Signed-off-by: Francesco Servidio <francesco.servidio@nordicsemi.no>
diff --git a/docs/release.md b/docs/release.md
index 197bbad..151943e 100644
--- a/docs/release.md
+++ b/docs/release.md
@@ -1,4 +1,4 @@
-# Release Process
+# Release process
 
 The following documents the release process used with MCUboot.
 
@@ -18,13 +18,13 @@
 We mark in documentation an MCUboot development version using
 the format MAJOR.MINOR.PATCH-dev.
 
-## Release Notes
+## Release notes
 
 Before making a release, be sure to update the `docs/release-notes.md`
 to describe the release.  This should be a high-level description of
 the changes, not a list of the git commits.
 
-## Release Candidates
+## Release candidates
 
 Prior to each release, tags are made (see below) for at least one
 release candidate (a.b.c-rc1, followed by a.b.c-rc2, etc, followed by
@@ -35,7 +35,7 @@
 that should be merged into main are those to fix bugs found in the
 rc and Mynewt metadata as described in the next section.
 
-## imgtool release
+## Imgtool release
 
 imgtool is released through pypi.org (The Python package index) and
 requires that its version to be updated by editing
@@ -57,7 +57,7 @@
 new release version, including updates to the pseudo keys
 (`*-(latest|dev)`).
 
-## Tagging and Release
+## Tagging and release
 
 To make a release, make sure your local repo is on the tip version by
 fetching from origin.  Typically, the releaser should create a branch
@@ -85,7 +85,7 @@
 git push origin va.b.c-rcn
 ```
 
-## Branching after a Release
+## Branching after a release
 
 After the final (non-`rc`) a.b.0 release is made, a new branch must
 be created and pushed: