Add snippet commands (#18453)

Closes #17860
Closes #15403

Release Notes:

- Added `snippets: configure snippets` command to create and modify
snippets
- Added `snippets: open folder` command for opening the
`~/.config/zed/snippets` directory


https://github.com/user-attachments/assets/fd9e664c-44b1-49bf-87a8-42b9e516f12f

crates/snippets_ui/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "snippets_ui"
+version = "0.1.0"
+edition = "2021"
+publish = false
+license = "GPL-3.0-or-later"
+
+[lints]
+workspace = true
+
+[lib]
+path = "src/snippets_ui.rs"
+
+[dependencies]
+fuzzy.workspace = true
+gpui.workspace = true
+language.workspace = true
+paths.workspace = true
+picker.workspace = true
+ui.workspace = true
+util.workspace = true
+workspace.workspace = true