chore: simplify the templates

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -4,12 +4,9 @@ about: 'Create a report to help us improve'
 labels: 'Bug :bug:'
 ---
 
-Please:
+## Bug Description
 
-- [ ] Check for duplicate issues. Please file separate requests as separate issues.
-- [ ] Describe how to reproduce the bug.
-- [ ] Use the latest versions of Vega and Vega-Lite.
-- [ ] Provide an [minimal, reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) spec in JSON, wrapped by triple backticks like this:
+Describe how to reproduce this bug. Provide an [minimal, reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) spec in JSON, wrapped by triple backticks like this:
 
 ```json
 {
@@ -18,4 +15,8 @@ Please:
 }
 ```
 
-- [ ] If applicable, include error messages and screenshots, GIF videos (e.g. using https://www.cockos.com/licecap/), or working examples (e.g. by clicking share in the [Vega-Editor](https://vega.github.io/editor/) or https://bit.ly/vega-lite-blocks)
+If applicable, include error messages and screenshots, videos, or working examples (e.g. by clicking share in the [Vega-Editor](https://vega.github.io/editor/).
+
+## Checklist
+
+- [ ] I checked for duplicate issues.

.github/ISSUE_TEMPLATE/Enhancement.md

@@ -4,11 +4,11 @@ about: 'Suggest a new idea or improvement for Vega-Lite'
 labels: 'Enhancement :tada:'
 ---
 
-Please:
+## Enhancement Description
 
-- [ ] Check for duplicate issues. Please file separate requests as separate issues on GitHub.
-- [ ] Describe the feature's goal, motivating use cases, and its expected behavior.
-- [ ] If you are proposing a new syntax, please provide at least one example spec, wrapped by triple backticks like this:
+Describe the feature's goal, motivating use cases, and its expected behavior.
+
+If you are proposing a new syntax, please provide at least one example spec, wrapped by triple backticks like this:
 
 ```json
 {
@@ -19,4 +19,6 @@ Please:
 
 You are encouraged to prototype multiple alternative syntaxes for your proposed feature. Doing so often leads to a better design.
 
-- [ ] If applicable, include screenshots, GIF videos (e.g. using https://www.cockos.com/licecap/), or working example (e.g. example Vega specification for the requested feature)
+## Checklist
+
+- [ ] I checked for duplicate issues.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,14 +1,13 @@
-Please:
+## PR Description
 
-- [ ] Make the pull requests (PRs) atomic (fix one issue at a time). Multiple relevant issues that must be fixed together? Make atomic commits so we can easily review each issue.
-- [ ] Provide a concise title as a [semantic commit message](https://www.conventionalcommits.org/) (e.g. "fix: correctly handle undefined properties") so we can easily copy it to the release note.
-  - Use imperative mood and present tense.
-- Mention relevant issues in the description (e.g., `Fixes #1` / `Fixes part of #1`).
-- [ ] Lint and test (Run `yarn test`).
-- [ ] Review your changes before sending the PR (to ensure code quality).
+## Checklist
+
+- [ ] This PR is atomic (i.e., it fixes one issue at a time).
+- [ ] The title is a concise [semantic commit message](https://www.conventionalcommits.org/) (e.g. "fix: correctly handle undefined properties").
+- [ ] `yarn test` runs successfully
 - For new features:
-  - [ ] Add new unit tests.
-  - [ ] Update the documentation under `site/docs/` + add examples.
+  - [ ] Has unit tests.
+  - [ ] Has documentation under `site/docs/` + examples.
 
 Tips: