style(show): use show: lettre.with() instead of unnamed function

- Maybe more idiomatic… not sure actually

exemple.typ

@@ -1,7 +1,7 @@
 #import "lettre.typ": *
 #show link: strong
 
-#show: doc => lettre(
+#show: lettre.with(
   de: [
     Ex Péditeur,\
     12 rue des Sept Nains\
@@ -21,7 +21,6 @@
   post: [
     #emph("PS: Finalement, rien.")
   ],
-  doc
 )
 
 je soussigné, Ex Péditeur, atteste par la présente sur l’honneur que ce document

lettre.typ

@@ -17,13 +17,22 @@
   show raw: set text(font: "Inconsolata")
   show heading: set block(above: 1.4em, below: 1em)
 
+  let formatLieuDate(lieu, date) = {
+    let isDate = date.trim().len() > 0;
+    let isLieu = lieu.trim().len() > 0;
+    if isLieu [#lieu]
+    if isDate {
+      if isLieu [, ]
+      [le #date]
+    }
+  }
+
   grid(
     columns: (2fr, 1fr, 2fr),
     par(de),
     text[],
     text[
-      #lieu
-      #if date.trim().len() != 0 [, le #date ]
+      #formatLieuDate(lieu, date)
     ] + v(2em),
     text[],
     text[],

readme.md

@@ -3,13 +3,12 @@ A simple template for French letters for typst.
 ## Usage
 
 To create a letter, write a typst document while defining the following
-parameters, with the `lettre.typ` file in the same folder:
+parameters, with the [`lettre.typ`](./lettre.typ) file in the same folder:
 
 ```typst
 #import "lettre.typ": *
-#show link: strong
 
-#show: doc => lettre(
+#show: lettre.with(
   de: [
     Sender\
     Address
@@ -20,14 +19,13 @@ parameters, with the `lettre.typ` file in the same folder:
   ],
   objet: "subject of the letter", // optional
   date: "date of sending", // optional
-  lieu: "location",
+  lieu: "location", // optional
   introduction: "opening",
   cloture: "closing",
   signature: "signature",
   post: [
     post-letter (e.g., post-scriptum)
   ],
-  doc
 )
 ```