Update README.md to mention main branch

We're now using the local `main` branch to synchronize with the
upstream `master` branch.

Author: jonpryor

README.md

@@ -1,17 +1,21 @@
 # Xamarin notes
 
-The canonical repository (`upstream`) for this fork is https://android.googlesource.com/platform/external/sqlite/
-`master` branch here is kept in sync with the upstream, if you need to update you can do it by adding a remote and 
+The canonical repository (`upstream`) for this fork is
+https://android.googlesource.com/platform/external/sqlite/
+
+The `main` branch here is kept in sync with the upstream `master` branch,
+if you need to update you can do it by adding a remote and
 merging its master branch into ours:
 
     $ git remote add upstream https://android.googlesource.com/platform/external/sqlite/
     $ git fetch upstream
     $ git merge upstream/master
     $ git push
 
-We do not use the `master` branch for anything else than to keep it in sync with Google upstream. Whenever there's a
-need to update SQLite version a new branch named after the SQLite version should be created off of the `master` branch
-and the following procedure should be followed:
+We do not use the `main` branch for anything else than to keep it in sync with
+Google upstream.  Whenever there's a need to update SQLite version a new branch
+named after the SQLite version should be created off of the `main` branch and
+the following procedure should be followed:
 
    * After the branch is created, download the amalgamation zip from https://sqlite.org/download.html
    * Copy the new amalgamation files to both the `dist` and `dist/orig` directories