Setup SyntaxSuggest as default gem

Adds the `syntax_suggest` syntax error display tool to Ruby through the same mechanism as `error_highlight` and `did_you_mean`. Reference ticket: https://bugs.ruby-lang.org/issues/18159

close #4845

## What is syntax_suggest?

When a syntax error is raised by requiring a file, dead_end will use a combination of indentation and lexing to identify the problem.

> Note: Previously this tool was named `dead_end`. 

## Known issues

- SyntaxSearch's approach of showing syntax errors only works through integration with `require`, `load`, `autoload`, and `require_relative` (since it monkeypatches them to detect syntax errors). It does not work with direct Ruby file invocations https://github.com/zombocom/dead_end/issues/31.
  - This causes failure in the test suite (test_expected_backtrace_location_when_inheriting_from_basic_object_and_including_kernel) and confusion when inspecting backtraces if there's a different error when trying to require a file such as measuring memory (https://github.com/zombocom/syntax_suggest/issues/124#issuecomment-1006705016).
  - Discussed fix. We previously talked about opening up `SyntaxError` to be monkeypatched in the same way that other gems hook into `NoMethodError`. This is currently not possible and requires development work. When we last talked about it at RubyKaigi Nobu expressed an ability to make such a change.

1 files changed, 7 insertions, 0 deletions

diff --git a/gem_prelude.rb b/gem_prelude.rb
index 94ada316aa..f382021ca3 100644
--- a/gem_prelude.rb
+++ b/gem_prelude.rb
@@ -17,3 +17,10 @@ begin
 rescue LoadError
   warn "`did_you_mean' was not loaded."
 end if defined?(DidYouMean)
+
+begin
+  require 'syntax_suggest/core_ext'
+rescue LoadError
+  warn "`syntax_suggest' was not loaded."
+end if defined?(SyntaxSuggest)
+