localize Severity levels and columns menu of diagnostics panel

Author: JessicaBarh

packages/jupyterlab-lsp/src/features/diagnostics/diagnostics.ts

@@ -111,7 +111,7 @@ class DiagnosticsPanel {
         column.is_visible = !column.is_visible;
         widget.update();
       },
-      label: args => args['name'] as string,
+      label: args => this.trans.__(`${args['name']}`) as string,
       isToggled: args => {
         let column = get_column(args['name'] as string);
         return column.is_visible;

packages/jupyterlab-lsp/src/features/diagnostics/listing.tsx

@@ -169,7 +169,7 @@ export class DiagnosticsListing extends VDomRenderer<DiagnosticsListing.Model> {
       name: 'Severity',
       // TODO: use default diagnostic severity
       render_cell: row => (
-        <td key={3}>{DiagnosticSeverity[row.data.diagnostic.severity || 1]}</td>
+        <td key={3}>{trans.__(DiagnosticSeverity[row.data.diagnostic.severity || 1])}</td>
       ),
       sort: (a, b) =>
         a.data.diagnostic.severity > b.data.diagnostic.severity ? 1 : -1