Added test for check doc strings in crates.

#1856

crates/ra_syntax/src/algo.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 pub mod visit;
 
 use std::ops::RangeInclusive;

crates/ra_syntax/src/algo/visit.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{AstNode, SyntaxNode};
 
 use std::marker::PhantomData;

crates/ra_syntax/src/ast/generated.rs

@@ -1,4 +1,4 @@
-// Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`
+//! Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`
 
 use crate::{
     ast::{self, AstChildren, AstNode},

crates/ra_syntax/src/fuzz.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{validation, AstNode, SourceFile, TextRange, TextUnit};
 use ra_text_edit::AtomTextEdit;
 use std::str::{self, FromStr};

crates/ra_syntax/src/parsing/lexer.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{
     SyntaxKind::{self, *},
     TextUnit,

crates/ra_syntax/src/parsing/text_token_source.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use ra_parser::Token as PToken;
 use ra_parser::TokenSource;
 

crates/ra_syntax/src/parsing/text_tree_sink.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::mem;
 
 use ra_parser::{ParseError, TreeSink};

crates/ra_syntax/src/ptr.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::{iter::successors, marker::PhantomData};
 
 use crate::{AstNode, SyntaxKind, SyntaxNode, TextRange};

crates/ra_syntax/src/syntax_error.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::fmt;
 
 use ra_parser::ParseError;

crates/ra_syntax/src/validation.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 mod block;
 
 use rustc_lexer::unescape;

crates/ra_syntax/src/validation/block.rs

@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{
     ast::{self, AstNode, AttrsOwner},
     SyntaxError,