Ignore warnings from gem_prelude

With the latest `wasm-wasi`, the following warnings are shown on TryRuby.

```
`RubyGems' were not loaded.
`error_highlight' was not loaded.
`did_you_mean' was not loaded.
`syntax_suggest' was not loaded.
```

This warnings come from `gem_prelude.rb`.
https://github.com/ruby/ruby/blob/master/gem_prelude.rb

I assume this this is because the current usage of `ruby.wasm`
on TryRuby don't consider RubyGems and fails to load it.

We should change the structure of how to use `ruby.wasm` for fixing
this. But, this is just warnings and there are no other issues.
And, it seems that this warnings would not be shown in Ruby 3.5
ruby/ruby@4e303fd
ruby/ruby@e9dadf1

So I fixed to just silence those warnings.

Author: y-yagi

app/try_ruby.rb

@@ -17,6 +17,13 @@ class TryRuby
 
   DEFAULT_RUBY_ENGINE = "cruby-3.4.1"
 
+  GEM_PRELUDE_WARNINGS = [
+    "`RubyGems' were not loaded.",
+    "`error_highlight' was not loaded.",
+    "`did_you_mean' was not loaded.",
+    "`syntax_suggest' was not loaded."
+  ].freeze
+
   def self.start
     instance
   end
@@ -455,13 +462,24 @@ def log_error(err)
   end
 
   def print_to_output(str, term = "\n")
+    return if warnings_from_gem_prelude?(str)
     @output_buffer << str.to_s + term
     @output.value = @output_buffer.join
   end
 
   def output=(text)
     @output.value = text
   end
+
+  # TODO: This would be needless if only supports Ruby >= 3.5.
+  def warnings_from_gem_prelude?(str)
+    return false if str.nil? || str.empty?
+
+    trimmed_str = str.strip
+    GEM_PRELUDE_WARNINGS.include?(trimmed_str)
+  end
+
+  private
 end
 
 $window.on("dom:load") { TryRuby.start }