Add task to generate html from rdoc

Author: kateinoigakukun

.gitignore

@@ -7,4 +7,6 @@ dist
 wapm_packages
 
 .cache
-compile_commands.json
+compile_commands.json
+
+html

tasks/doc.rake

@@ -0,0 +1,8 @@
+require 'rdoc/task'
+require 'ruby_wasm/version'
+
+RDoc::Task.new do |doc|
+  doc.main = 'README.md'
+  doc.title = "ruby.wasm #{RubyWasm::VERSION} Documentation"
+  doc.rdoc_files = FileList.new %w[lib/**/*.rb ext/**/*.c ext/**/*.rb]
+end