Update INSTALL to mention mounting the engine and running migrations

[nickhammond]

No description provided.

[reidab]

This should be being handled by the calagator:install generator as part of the previous generation steps here:

https://github.com/calagator/calagator/blob/main/lib/generators/calagator/install_generator.rb#L26-L28

That said, I know there were some issues with the app template and the recent rails upgrade work, so it's possible the generator isn't being run correctly. If it's not, I wonder if it makes more sense to add a manual run of rails generate calagator:install to the README instead of adding the route manually?

[nickhammond]

Running that is throwing an error so that might've been why it didn't run and add it.

Rails 5.2.7.1

➜  events git:(main) ✗ bundle exec calagator install
rake aborted!
Don't know how to build task 'rails:template' (See the list of available tasks with `rake --tasks`)
/Users/nick/.gem/ruby/2.5.9/gems/rake-13.0.6/exe/rake:27:in `<top (required)>'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli/exec.rb:58:in `load'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli/exec.rb:58:in `kernel_load'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli/exec.rb:23:in `run'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli.rb:483:in `exec'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli.rb:31:in `dispatch'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/cli.rb:25:in `start'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/exe/bundle:48:in `block in <top (required)>'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/lib/bundler/friendly_errors.rb:103:in `with_friendly_errors'
/Users/nick/.gem/ruby/2.5.9/gems/bundler-2.3.13/exe/bundle:36:in `<top (required)>'
/Users/nick/.gem/ruby/2.5.9/bin/bundle:23:in `load'
/Users/nick/.gem/ruby/2.5.9/bin/bundle:23:in `<main>'
(See full trace by running task with --trace)

[evolve2k]

Anyone have suggestions on what next for this PR?