Update README.md in addons generator

lib/generators/addon/addon_generator.rb

@@ -176,7 +176,12 @@ class AddonGenerator < Rails::Generators::NamedBase
     copy_file('.gitignore', "addons/#{@addon_name}/.gitignore")
     copy_file('Gemfile', "addons/#{@addon_name}/Gemfile")
     copy_file('LICENSE.txt', "addons/#{@addon_name}/LICENSE.txt")
-    copy_file('README.md', "addons/#{@addon_name}/README.md")
+    file_path = "addons/#{@addon_name}/README.md"
+    copy_file('README.md', file_path)
+    gsub_file(file_path, '${ADDON_NAME}', @addon_name)
+    gsub_file(file_path, '${FULL_UNDERSCORE_NAME}', @full_underscore_name)
+    gsub_file(file_path, '${NAME}', name)
+    gsub_file(file_path, '${FOLDERS_PATH}', @folders_path)
 
     # Rakefile
     file_path = "addons/#{@addon_name}/Rakefile"

lib/generators/addon/templates/README.md

@@ -1 +1,35 @@
-# TODO
+# sciNote addon - `${ADDON_NAME}`
+
+## How to include this addon inside main sciNote application
+
+* Inside `Gemfile`, add the following reference:
+
+```ruby
+gem '${FULL_UNDERSCORE_NAME}',
+    path: 'addons/${ADDON_NAME}'
+```
+
+* Inside `config/routes.rb`, add the following reference:
+
+```ruby
+mount ${NAME}::Engine => '/'
+```
+
+* If you have any addon-specific JavaScript code, add the following reference inside `app/assets/javascripts/application.js.erb`:
+
+```js
+//= require ${FOLDERS_PATH}
+```
+
+* If you have any addon-specific CSS code, add the following reference inside `app/assets/stylesheets/application.scss` (starting comment):
+
+```css
+ *= require ${FOLDERS_PATH}/application
+```
+
+Then, do the following:
+
+1. Run `make docker`,
+2. Run `make cli` -> `rake db:migrate`,
+3. (optional) setup any addon initializers/settings,
+4. Start application (`make run`)!