[Eslint] Add a custom rule for enforcing `as const` in UIStrings

We needed to update other l10n related eslint rules and
`collect-strings` script to look for `as const` definitions as well.

Fixed: 397381592
Change-Id: Ia3eb9a97fa1595093fb332525f996039f7546d8e
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6287325
Commit-Queue: Ergün Erdoğmuş <[email protected]>
Reviewed-by: Nikolay Vitkov <[email protected]>
Reviewed-by: Mathias Bynens <[email protected]>
Reviewed-by: Simon Zünd <[email protected]>
diff --git a/front_end/panels/network/NetworkLogView.ts b/front_end/panels/network/NetworkLogView.ts
index d83c34d..26b9f75 100644
--- a/front_end/panels/network/NetworkLogView.ts
+++ b/front_end/panels/network/NetworkLogView.ts
@@ -465,7 +465,7 @@
    * @description Text for the Show only/Hide requests dropdown button of the filterbar
    */
   moreFilters: 'More filters',
-};
+} as const;
 const str_ = i18n.i18n.registerUIStrings('panels/network/NetworkLogView.ts', UIStrings);
 const i18nString = i18n.i18n.getLocalizedString.bind(undefined, str_);