Add continue-on-error true to ignore head/base commit issue

[latacora-tomekr]

Motivation

https://github.com/jitterbit/get-changed-files/blob/master/src/main.ts#L49-L53 checks that head and base match which isn't going to work well with how PR's get opened for this repository. The action still works and correctly displays the modified files so we can add continue-on-error: true to skip this issue.

See also jitterbit/get-changed-files#11

Examples:

• https://github.com/alex/nyt-2020-election-scraper/pull/146/checks?check_run_id=1361936132#step:5:10
• https://github.com/alex/nyt-2020-election-scraper/pull/147/checks?check_run_id=1361939259#step:5:10

Changes

Use continue-on-error: true for the get-changed-files PR step.

• Ensured that relevant issues are linked, if this PR resolves any outstanding.
• Added a screenshot for all UI changes (you can drag the file into this edit box and it will be uploaded).
• Ensured that changes to auto-generated files have not been committed; in particular, *.html, *.csv and *.json files.

[bojanrajkovic]

As discussed, let's close this one and add a "Have you rebased?" checkbox to the PR template.