feat: make expression persistent in the overpass importer (#2339)

In other words: fill in the "tags" input with the latest typed
expression.

Otherwise, when making tries with overpass imports, one have to type it
again and again (it's available through the autocomplete, though, but
it's not obvious and it's less friendly IMHO).

umap/static/umap/js/modules/importers/overpass.js

@@ -53,11 +53,15 @@ export class Importer {
       'https://photon.komoot.io/api?q={q}&layer=county&layer=city&layer=state'
     this.id = 'overpass'
     this.boundaryChoice = null
+    this.expression = null
   }
 
   async open(importer) {
     const container = DomUtil.create('div')
     container.innerHTML = TEMPLATE
+    if (this.expression) {
+      container.querySelector('[name=tags]').value = this.expression
+    }
     this.autocomplete = new Autocomplete(container.querySelector('#area'), {
       url: this.searchUrl,
       placeholder: translate(
@@ -80,6 +84,7 @@ export class Importer {
         Alert.error(translate('Expression is empty'))
         return
       }
+      this.expression = form.tags
       let tags = form.tags
       if (!tags.startsWith('[')) tags = `[${tags}]`
       let area = '{south},{west},{north},{east}'