Implement highlighting ourselves to remove syntect dep

Cargo.toml

@@ -24,12 +24,12 @@ fs-err = "2.6.0"
 futures = "0.3.19"
 http = "0.2.6"
 iter-set = "2.0.2"
-memchr = "2.4.1"
 once_cell = "1.9.0"
 open = "2.0.2"
 prost = "0.9.0"
 prost-reflect = { version = "0.5.1", features = ["serde"] }
 rand = "0.8.4"
+regex = "1.5.4"
 rustls = { version = "0.19.1", features = ["dangerous_configuration"] }
 serde-transcode = "1.1.1"
 serde_json = "1.0.74"
@@ -54,11 +54,6 @@ features = ["transport", "tls", "tls-roots", "compression"]
 version = "1.15.0"
 features = ["rt-multi-thread", "sync", "fs"]
 
-[dependencies.syntect]
-version = "4.6.0"
-default-features = false
-features = ["parsing", "regex-onig", "assets", "dump-load"]
-
 [dependencies.serde]
 version = "1.0.133"
 features = ["derive", "rc"]
@@ -78,3 +73,6 @@ anyhow = "1.0.52"
 version = "6.0.0"
 default-features = false
 features = ["git"]
+
+[patch.crates-io]
+piet = { git = "https://github.com/linebender/piet", branch = "master" }