Fix regular expressions in workflows (#103)

* Escape `[]` and `()` completely

* Avoid unnecessary escapes

* Tolerate tab for whitespace

* Tolerate other list markers

* Tolerate form-feed for whitespace in task lists

.github/workflows/1-add-headers.yml

@@ -59,7 +59,7 @@ jobs:
  uses: skills/action-check-file@v1
  with:
  file: "index.md"
- search: "# [a-zA-Z0-9]"
+ search: "(?<!#)#{1,6}([\ \\t](.*))?$"
 
  # In README.md, switch step 1 for step 2.
  - name: Update to step 2

.github/workflows/2-add-an-image.yml

@@ -59,7 +59,7 @@ jobs:
  uses: skills/action-check-file@v1
  with:
  file: "index.md"
- search: "\\!\\[.*](.*)"
+ search: "\\!\\[.*\\]\\(.*\\)"
 
  # In README.md, switch step 2 for step 3.
  - name: Update to step 3

.github/workflows/3-add-a-code-example.yml

@@ -59,7 +59,7 @@ jobs:
  uses: skills/action-check-file@v1
  with:
  file: "index.md"
- search: "\\`\\`\\`"
+ search: "```"
 
  # In README.md, switch step 3 for step 4.
  - name: Update to step 4

.github/workflows/4-make-a-task-list.yml

@@ -59,7 +59,7 @@ jobs:
  uses: skills/action-check-file@v1
  with:
  file: "index.md"
- search: "\\- \\[ ] "
+ search: "([\\-\\+\\*]|[0-9]+\\.)[\ \\t]+\\[[\ \\t\\fxX]\\][\ \\t\\f]+\\S.*$"
 
  # In README.md, switch step 4 for step 5.
  - name: Update to step 5