fix: autocomplete supports adding extensions

[axetroy]

close #138

Typescript does not add extensions by default for cached modules when import from autocomplete

- import { foo } from "./bar"
+ import { foo } from "./bar.ts"

Now it has been fixed

/cc @ry @bartlomieju

before

after

 PASS  core/deno_normalize_import_statement.test.ts
 PASS  core/deno_deps.test.ts
 PASS  core/deno_type_hint.test.ts
 PASS  core/cache.test.ts
 PASS  core/import_map.test.ts
 PASS  core/module_resolver.test.ts
 PASS  core/cache_map.test.ts
 PASS  core/file_walker.test.ts
 PASS  core/extension.test.ts
 PASS  core/configuration.test.ts
 PASS  core/deno_cache.test.ts
 PASS  core/deno.test.ts
 PASS  core/util.test.ts
 PASS  core/hash_meta.test.ts
------------------------------------|---------|----------|---------|---------|-------------------
File                                | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
------------------------------------|---------|----------|---------|---------|-------------------
All files                           |     100 |      100 |     100 |     100 |                   
 cache.ts                           |     100 |      100 |     100 |     100 |                   
 cache_map.ts                       |     100 |      100 |     100 |     100 |                   
 configuration.ts                   |     100 |      100 |     100 |     100 |                   
 deno.ts                            |     100 |      100 |     100 |     100 |                   
 deno_cache.ts                      |     100 |      100 |     100 |     100 |                   
 deno_deps.ts                       |     100 |      100 |     100 |     100 |                   
 deno_normalize_import_statement.ts |     100 |      100 |     100 |     100 |                   
 deno_type_hint.ts                  |     100 |      100 |     100 |     100 |                   
 extension.ts                       |     100 |      100 |     100 |     100 |                   
 file_walker.ts                     |     100 |      100 |     100 |     100 |                   
 hash_meta.ts                       |     100 |      100 |     100 |     100 |                   
 import_map.ts                      |     100 |      100 |     100 |     100 |                   
 module_resolver.ts                 |     100 |      100 |     100 |     100 |                   
 util.ts                            |     100 |      100 |     100 |     100 |                   
------------------------------------|---------|----------|---------|---------|-------------------

[axetroy]

Since we cannot know the actual module from import { foo } from "./bar"

So we can only guess based on commonly used extensions until they match

[lucacasonato]

Thanks @axetroy - this is a very nice addition. I tested it locally and it works exactly as expected 👍

[lucacasonato]

LGTM - thanks @axetroy!