package.json: recognize *.*tmpl as go template files

filenamePatterns allows glob matching.
Gopls processes any '.*tmpl' files as go template file.

For #609

Change-Id: I73334c1fdb7d23544591bbbdb5a3ad78397fa227
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/342069
Trust: Hyang-Ah Hana Kim <[email protected]>
Trust: Peter Weinberger <[email protected]>
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
TryBot-Result: kokoro <[email protected]>
Reviewed-by: Peter Weinberger <[email protected]>

Author: hyangah

package.json

@@ -129,7 +129,7 @@
       },
       {
         "id": "go.mod",
-        "extensions": [
+        "filenames": [
           "go.mod",
           "gopls.mod",
           "go.work"
@@ -141,7 +141,7 @@
       },
       {
         "id": "go.sum",
-        "extensions": [
+        "filenames": [
           "go.sum"
         ],
         "aliases": [
@@ -150,8 +150,8 @@
       },
       {
         "id": "tmpl",
-        "extensions": [
-          ".tmpl"
+        "filenamePatterns": [
+          "*.*tmpl"
         ],
         "aliases": [
           "Go Template File"