Syncing from original

CONTRIBUTING.md

@@ -46,7 +46,7 @@ In between these clear-cut categories, there is some gray area. Please feel free
 
 Due to the long legacy of the existing text the guidelines below are not always applied. We do require that you apply the guidelines when making changes, though are happy to provide assistance if this proves to be a blocker to you.
 
-Use a column width of 100 characters and add newlines where whitespace is used. (Emacs, set `fill-column` to `100`; in Vim, set `textwidth` to `100`; and in Sublime, set `wrap_width` to `100`.)
+Use a column width of 100 characters and add newlines where whitespace is used. (Emacs, set `fill-column` to `100`; in Vim, set `textwidth` to `100`; and in Sublime, set `wrap_width` to `100`. Alternatively, wrap the paragraph(s) with your changes with https://domenic.github.io/rewrapper/. Make sure that `column length to rewrap` is set to 100.)
 
 Using newlines between "inline" element tag names and their content is forbidden. (This actually alters the content, by adding spaces.) That is,
 ```html

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,15 @@
+<!--
+Thank you for contributing to the HTML Standard! Please describe the change you are making and complete the checklist below if your change is not editorial.
+-->
+
+- [ ] At least two implementers are interested (and none opposed):
+   * …
+   * …
+- [ ] [Tests](https://github.com/web-platform-tests/wpt) are written and can be reviewed and commented upon at:
+   * …
+- [ ] [Implementation bugs](https://github.com/whatwg/meta/blob/master/MAINTAINERS.md#handling-pull-requests) are filed:
+   * Chrome: …
+   * Firefox: …
+   * Safari: …
+
+(See [WHATWG Working Mode: Changes](https://whatwg.org/working-mode#changes) for more details.)