railsrc: Add application template (#747)

Now that [Suspenders 3.0.0][] has [merged][], we can improve the
developer experience by placing all options into our `railsrc` file.

Once this commit it merged, we can link to our dotfiles from the
Suspenders README.

Also closes #746

[Suspenders 3.0.0]: https://github.com/thoughtbot/suspenders
[merged]: thoughtbot/suspenders#1135

README.md

@@ -216,11 +216,18 @@ configuration:
 
 [Rails](https://rubyonrails.org)
 
-- Adds [railsrc][] with `--database=postgresql`. If you need to use another
-  database, you can override this value like so: `rails new my_app --database=mysql` or
-`rails new my_app --no_rc`
+- Adds [railsrc][] with the following options to integrate with [Suspenders][].
+
+```
+--database=postgresql
+--skip-test
+-m=https://raw.githubusercontent.com/thoughtbot/suspenders/main/lib/install/web.rb
+```
+
+If you want to skip this file altogether, run `rails new my_app --no_rc`.
 
 [railsrc]: https://github.com/rails/rails/blob/7f7f9df8641e35a076fe26bd097f6a1b22cb4e2d/railties/lib/rails/generators/rails/app/USAGE#L5C1-L7
+[Suspenders]: https://github.com/thoughtbot/suspenders
 
 Shell aliases and scripts:
 

railsrc

@@ -1,2 +1,3 @@
 --database=postgresql
 --skip-test
+-m=https://raw.githubusercontent.com/thoughtbot/suspenders/main/lib/install/web.rb