Reword message:more detail about declaration files

Author: sandersn

src/compiler/checker.ts

@@ -1642,7 +1642,7 @@ namespace ts {
                 }
                 else if (noImplicitAny && moduleNotFoundError) {
                     let errorInfo = chainDiagnosticMessages(/*details*/ undefined,
-                        Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_adding_declare_module_0_in_a_separate_file,
+                        Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_add_a_new_declaration_d_ts_file_containing_declare_module_0,
                         moduleReference);
                     errorInfo = chainDiagnosticMessages(errorInfo,
                         Diagnostics.Could_not_find_a_declaration_file_for_module_0_1_implicitly_has_an_any_type,

src/compiler/diagnosticMessages.json

@@ -3310,7 +3310,7 @@
         "category": "Error",
         "code": 7034
     },
-    "Try `npm install @types/{0}` if it exists or adding `declare module '{0}'` in a separate file.": {
+    "Try `npm install @types/{0}` if it exists or add a new declaration (.d.ts) file containing `declare module '{0}';`": {
         "category": "Error",
         "code": 7035
     },

tests/baselines/reference/untypedModuleImport_noImplicitAny.errors.txt

@@ -1,12 +1,12 @@
 /a.ts(1,22): error TS7016: Could not find a declaration file for module 'foo'. '/node_modules/foo/index.js' implicitly has an 'any' type.
-  Try `npm install @types/foo` if it exists or adding `declare module 'foo'` in a separate file.
+  Try `npm install @types/foo` if it exists or add a new declaration (.d.ts) file containing `declare module 'foo';`
 
 
 ==== /a.ts (1 errors) ====
     import * as foo from "foo";
                          ~~~~~
 !!! error TS7016: Could not find a declaration file for module 'foo'. '/node_modules/foo/index.js' implicitly has an 'any' type.
-!!! error TS7016:   Try `npm install @types/foo` if it exists or adding `declare module 'foo'` in a separate file.
+!!! error TS7016:   Try `npm install @types/foo` if it exists or add a new declaration (.d.ts) file containing `declare module 'foo';`
 
 ==== /node_modules/foo/index.js (0 errors) ====
     // This tests that `--noImplicitAny` disables untyped modules.