feat(omp): nix shell

oh-my-posh/basic-nerd.toml

@@ -33,6 +33,15 @@ final_space = true
     [blocks.segments.properties]
       cache_duration = 'none'
 
+  [[blocks.segments]]
+    style = 'plain'
+    type = 'command'
+    template = '{{ if .Output }}() {{ end }}'
+    [blocks.segments.properties]
+      shell = 'bash'
+      command = "echo $PATH | grep -qc /nix/store && echo true"
+      interpret = false
+
   [[blocks.segments]]
     foreground = 'white'
     type = 'path'

oh-my-posh/basic.toml

@@ -27,6 +27,15 @@ final_space = true
     template = '{{ if .SSHSession }}(SSH) {{ end }}'
     type = 'session'
 
+  [[blocks.segments]]
+    style = 'plain'
+    type = 'command'
+    template = '{{ if .Output }}(Nix-Shell) {{ end }}'
+    [blocks.segments.properties]
+      shell = 'bash'
+      command = "echo $PATH | grep -qc /nix/store && echo true"
+      interpret = false
+
   [[blocks.segments]]
     style = 'plain'
     foreground = 'white'