Update .gitignore and README.md

* Descriptions for C extension stuff
* README list of `mygem` occurences
* `.gitignore` Visual Studio and `tmp/`

Author: ParadoxV5

.gitignore

@@ -1,9 +1,12 @@
 # VSCode
 /.vscode/
+# Visual Studio
+/.vs/
 # JetBrains
 /.idea/
 
 # Ruby
+/tmp/
 /Gemfile.lock
 # https://github.com/ruby/gem_rbs_collection
 /.gem_rbs_collection/

README.md

@@ -1,19 +1,23 @@
 # `template-ruby-gem`
 
 Built upon [`ParadoxV5/mygem`](https://github.com/ParadoxV5/mygem),
-this is a moderate yet thorough template for a Ruby Gem project.
-Note: just `gem`. The `rake` is for invoking minitest (See [§Rakefile](#Rakefile).
+this is a moderate yet thorough template for a Ruby C extension project.
+Note: just `gem`. The `rake` is for test-building and invoking minitest (See [§Rakefile](#Rakefile).
 
 
 ## How to Setup
 
 * Rename all occurrences of `mygem`, lower- or title-case, with the name of your epic Gem.
+  * [`ext/mygem/`](ext/mygem/)
+  * [`ext/mygem/mygem.c` and Line 3](ext/mygem/mygem.c#L3)
+  * [`ext/mygem/extconf.rb` Line 6](ext/mygem/extconf.rb#L6)
   * [`lib/mygem/`](lib/mygem/)
   * [`lib/mygem.rb` and Line 1 & 2](lib/mygem.rb#L1-2)
   * [`lib/mygem/version.rb Line 3`](lib/mygem/version.rb#L3)
   * [`sig/mygem.rbs` and Line 1](sig/mygem.rbs#L1)
   * [`test/mygem_test.rb` and Lines 3 & 4](test/mygem_test.rb#L3-4)
   * [`mygem.gemspec` and Lines 2, 5 & 7](mygem.gemspec#L2-L7)
+  * [`Rakefile` Lines 12 & 15](Rakefile#L12-L15)
 * Update the [`gemspec`](mygem.gemspec) with your Gem’s information. (See [§`*.gemspec`](#gemspec))
 * Overwrite this `README` with an introduction to your epic project.
 * Replace *this template’s* [`LICENSE.txt`](LICENSE.txt) with
@@ -28,9 +32,15 @@ Note: just `gem`. The `rake` is for invoking minitest (See [§Rakefile](#Rakefil
 Follow [the convention](https://guides.rubygems.org/patterns/#file-names) regarding the file structure:
 
 
+### [`ext/**`](ext/)
+
+This is the folder where people put their C sources under a sub-folder,
+including the [init. function](ext/mygem/mygem.c) and the [config script](ext/mygem/extconf.rb).
+Third-party headers can be in `ext/include` for organization.
+
 ### [`lib/**`](lib/)
 
-This is the folder where people put their Gem sources, starting with their
+This is the folder where people put their Ruby sources, starting with their
 [entry script](lib/mygem.rb) right under `lib` and the rest in a sub-folder.
 
 
@@ -72,6 +82,8 @@ See [§License](#License)
 
 The cool li’l testing toolkit minitest does not come with an executable,
 but rather a Ruby API that generates a handful of [Rake](https://github.com/ruby/rake) tasks.
+While we are at it, we might as well include [`rake-compiler`](https://github.com/rake-compiler/rake-compiler/actions)
+to automate compiling C during development.
 
 
 ### [`README.md`](README.md)
@@ -87,17 +99,17 @@ Inside this folder are small but thoroughly configured ([minimal modification](#
 #### [`documentation.yml`](.github/workflows/documentation.yml)
 Generate [YARD docs](https://yardoc.org) and
 [publish to GitHub Pages](https://github.blog/changelog/2022-07-27-github-pages-custom-github-actions-workflows-beta)
-after the `main` branch receives an update in the Ruby sources ([`lib/`](lib/)) folder.
+after the `main` branch receives an update in the sources ([`ext/`](ext/) & [`lib/`](lib/)) folders.
 
 #### [`test.yml`](.github/workflows/test.yml)
 Run tests independently (`rake test:isolated`) after any branch receives an update
 on the [`.gemspec`](mygem.gemspec) (in the event of library version changes) or
-in the sources ([`lib`](lib/)) or test ([`test`](test/)) folders.
+in the sources ([`ext`](ext/) & [`lib/`](lib/)) or test ([`test`](test/)) folders.
 
 #### [`type_check.yml`](.github/workflows/type_check.yml)
 Check your RBS appendices (see [§sig/**](#sig)) after any branch receives an update
 on the [`.gemspec`](mygem.gemspec) (in the event of library version changes) or
-in the sources ([`lib`](lib/)) or signature ([`sig`](sig/)) folders.
+in the Ruby ([`lib`](lib/)) or signature ([`sig`](sig/)) folders.
 
 #### [`package.yml`](.github/workflows/package.yml)
 Publish to RubyGems after the GitHub repo publishes a Release. This workflow requires a “Push rubygem”