fix(cc-addon-admin): avoid focus loss during API calls

Rely on `readonly` instead of `disabled` during API calls so that focus
is maintained on the input if the user has submitted with the `Enter`
key.

Fixes #1102

src/components/cc-addon-admin/cc-addon-admin.js

@@ -134,7 +134,7 @@ export class CcAddonAdmin extends LitElement {
           <cc-input-text
             label="${i18n('cc-addon-admin.input.name')}"
             ?skeleton=${isSkeleton}
-            ?disabled=${isFormDisabled}
+            ?readonly=${isFormDisabled}
             .value=${this._name}
             @cc-input-text:input=${this._onNameInput}
             @cc-input-text:requestimplicitsubmit=${this._onNameSubmit}
@@ -157,7 +157,7 @@ export class CcAddonAdmin extends LitElement {
           <cc-input-text
             label="${i18n('cc-addon-admin.input.tags')}"
             ?skeleton=${isSkeleton}
-            ?disabled=${isFormDisabled}
+            ?readonly=${isFormDisabled}
             .tags=${this._tags}
             placeholder="${i18n('cc-addon-admin.tags-empty')}"
             @cc-input-text:tags=${this._onTagsInput}