add Readme.md to tidy

update Readme

add info about githooks and bootstrap.toml

add info about config and remove linting specific files

add link to rustc-dev-guide

src/tests/intro.md

diff --git a/src/tests/intro.md b/src/tests/intro.md
index b90c16d..4fa63b8 100644
--- a/src/tests/intro.md
+++ b/src/tests/intro.md
@@ -70,10 +70,12 @@
 
 Tidy is a custom tool used for validating source code style and formatting
 conventions, such as rejecting long lines. There is more information in the
-[section on coding conventions](../conventions.md#formatting).
+[section on coding conventions](../conventions.md#formatting) or the [Tidy Readme].
 
 > Examples: `./x test tidy`
 
+[Tidy Readme]: https://github.com/rust-lang/rust/blob/master/src/tools/tidy/Readme.md
+
 
 ### Formatting