Add security workflow (1/2): GoSec scan

[kxyr]

Motivation

Follow up to issue open-telemetry/oteps#144

GoSec is a static analysis engine which scans go source code for security vulnerabilities. As the project grows and we near GA it might be useful to have a workflow which checks for security vulnerabilities so we can ensure every incremental change is following best development practices. Also passing basic security checks will also make sure that there aren't any glaring issues for our users.

Changes

This PR adds GoSec security checks to the repo

• After every run the workflow uploads the results to GitHub. Details on the run and security alerts will show up in the security tab of this repo.

Workflow Triggers

• daily cron job at 1:30am
• workflow_dispatch (in case maintainers want to trigger a security check manually)

cc @alolita

[kxyr]

Closing this as gosec is already linted in CI tests here