Add triomphe

As we'll put offsets into children array, we won't be able to use the
union trick. So lets use weakless arc instead!

Author: matklad

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rowan"
-version = "0.11.0-pre.1"
+version = "0.10.1"
 authors = ["Aleksey Kladov <[email protected]>"]
 repository = "https://github.com/rust-analyzer/rowan"
 license = "MIT OR Apache-2.0"
@@ -10,10 +10,12 @@ edition = "2018"
 [dependencies]
 erasable = "1.2.1"
 rustc-hash = "1.0.1"
-serde = { version = "1.0.89", optional = true, default-features = false }
 slice-dst = "1.4.1"
 smol_str = "0.1.10"
 text-size = "1.0.0"
+triomphe = "0.1.1"
+
+serde = { version = "1.0.89", optional = true, default-features = false }
 
 [dev-dependencies]
 m_lexer = "0.0.4"