Add golang-otel template

[welteki]

Description

Add the official golang-otel template to the function store.

How has this been tested

Verified the output of faas-cli template store list:

faas-cli template store list --url https://raw.githubusercontent.com/welteki/store/refs/heads/golang-otel/templates.json

NAME                     RECOMMENDED DESCRIPTION        SOURCE
golang-middleware        [x]         openfaas           HTTP middleware interface in Go
golang-http              [ ]         openfaas           Request/response style HTTP template
golang-otel              [ ]         openfaas           HTTP middleware interface in Go with OpenTelemetry support

Other languages are omitted from the output.