Trigger workflow_dispatch requires users to pass GITHUB_TOKEN

[SebastianMorawiec]

I've tried using github-action-benchmark workflow with workflow_dispatch trigger, but for security reasons I do not want to pass secrets.GITHUB_TOKEN as input argument to github-token.

Due to the change done here:
https://github.com/benchmark-action/github-action-benchmark/pull/74/files

If the workflow trigger is not or , the benchark-workflow tried to use GITHUB_TOKEN to parse some commit information. If no GITHUB_TOKEN is provided, it asserts out
Details of the root-cause:

github-action-benchmark/src/extract.ts

Line 300 in deaf0e0

if (!githubToken) {

(github.context.payload.head_commit is only set on push trigger)

The commit context should be either:

1. Being figured out based on the payload available in workflow_dispatch trigger
2. Or I should be able to pass the input to omit this data entirely