feat(module): Add a meson devenv indicator (#4389)

* feat(module): Add a meson devenv indicator

Adds a Meson Developer Environment indicator, if the MESON_DEVENV
variable is set. Inside a `meson devenv`, the prompt will include the
current Meson project name

This also contains a new Truncate utility function, which may be adapted for other modules in the future

* docs: Add Meson to presets

src/configs/mod.rs

@@ -46,6 +46,7 @@ pub mod line_break;
 pub mod localip;
 pub mod lua;
 pub mod memory_usage;
+pub mod meson;
 pub mod nim;
 pub mod nix_shell;
 pub mod nodejs;
@@ -184,6 +185,8 @@ pub struct FullConfig<'a> {
     #[serde(borrow)]
     memory_usage: memory_usage::MemoryConfig<'a>,
     #[serde(borrow)]
+    meson: meson::MesonConfig<'a>,
+    #[serde(borrow)]
     nim: nim::NimConfig<'a>,
     #[serde(borrow)]
     nix_shell: nix_shell::NixShellConfig<'a>,