feat(CI): add the GitHub Super Linter

The GitHub Super Linter is a more robust and better supported
tool than the current GitHub Actions we are using.

Running these checks:

ERROR_ON_MISSING_EXEC_BIT: true
VALIDATE_BASH: true
VALIDATE_BASH_EXEC: true
VALIDATE_EDITORCONFIG: true
VALIDATE_MARKDOWN: true
VALIDATE_SHELL_SHFMT: true
VALIDATE_YAML: true

https://github.com/marketplace/actions/super-linter
https://github.com/github/super-linter

Added the GitHub Super Linter badge to the README.

Also updated the pre-commit framework and added
more documentation on pre-commit.

Added one more pre-commit check: check-executables-have-shebangs

Added one extra check for merge conflicts to our
GitHub Actions.

EditorConfig and Markdown linting.

Minor grammar and spelling fixes.

Update linter.yml

2 files changed, 26 insertions, 26 deletions

diff --git a/mrbgems/mruby-method/README.md b/mrbgems/mruby-method/README.md
index eef414c55..f299718df 100644
--- a/mrbgems/mruby-method/README.md
+++ b/mrbgems/mruby-method/README.md
@@ -23,38 +23,38 @@ end
 
 ## Kernel
 
-- `Kernel#method`
-- `Kernel#singleton_method`
+* `Kernel#method`
+* `Kernel#singleton_method`
 
 ## Module
 
-- `Module#instance_method`
+* `Module#instance_method`
 
 ## Method class
 
-- `Method#name`
-- `Method#call`
-- `Method#super_method`
-- `Method#arity`
-- `Method#unbind`
-- `Method#[]`
-- `Method#owner`
-- `Method#receiver`
-- `Method#parameters`
-- `Method#source_location`
-- `Method#to_proc`
+* `Method#name`
+* `Method#call`
+* `Method#super_method`
+* `Method#arity`
+* `Method#unbind`
+* `Method#[]`
+* `Method#owner`
+* `Method#receiver`
+* `Method#parameters`
+* `Method#source_location`
+* `Method#to_proc`
 
 ## UnboundMethod class
 
-- `UnboundMethod#name`
-- `UnboundMethod#bind`
-- `UnboundMethod#super_method`
-- `UnboundMethod#arity`
-- `UnboundMethod#owner`
-- `UnboundMethod#parameters`
-- `UnboundMethod#source_location`
+* `UnboundMethod#name`
+* `UnboundMethod#bind`
+* `UnboundMethod#super_method`
+* `UnboundMethod#arity`
+* `UnboundMethod#owner`
+* `UnboundMethod#parameters`
+* `UnboundMethod#source_location`
 
 # See also
 
-- https://ruby-doc.org/core-2.3.3/Method.html
-- https://ruby-doc.org/core-2.3.3/UnboundMethod.html
+* <https://ruby-doc.org/core-2.3.3/Method.html>
+* <https://ruby-doc.org/core-2.3.3/UnboundMethod.html>
diff --git a/mrbgems/mruby-method/test/method.rb b/mrbgems/mruby-method/test/method.rb
index 123ae34be..a7db20031 100644
--- a/mrbgems/mruby-method/test/method.rb
+++ b/mrbgems/mruby-method/test/method.rb
@@ -92,9 +92,9 @@ assert 'Method#call' do
   assert_equal 42, klass2.new.method(:foo).call
 
   i = Class.new {
-   def bar
-     yield 3
-   end
+    def bar
+      yield 3
+    end
   }.new
   assert_raise(LocalJumpError) { i.method(:bar).call }
   assert_equal 3, i.method(:bar).call { |i| i }