Update project tooling & config

[thibaudcolas]

• More badges
• Adds a basic CI pipeline, with just the Node tooling running for now
• Defines the project’s Node dependencies (updated from 8 or 10 to 14)
• Ignores compiled static files in git
• Switches from node-sass to Dart sass to make the tooling more portable
• Adds the missing autoprefixer setup
• Cleans up unused dependencies
• Add basic documentation for contributors / maintainers.

The only user-facing change should be the addition of vendor prefixes for the CSS. This seems to have been an issue for IE11 and Safari users in particular.

@@ -1,6 +1,8 @@
.c-sf-add-button {
  width: 100%;
  height: 34px;
+  -webkit-appearance: none;
+  -moz-appearance: none;
  appearance: none;
  border: 0 none;
  color: #007d7e;
@@ -9,8 +11,12 @@
  padding: 0;
  cursor: pointer;
  outline: none;
+  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  overflow: hidden;
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
  user-select: none;
  opacity: 0;
  pointer-events: none;
@@ -37,6 +43,9 @@
  position: relative;
  padding: 7.5px 0 30px;
  border-radius: 3px;
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
  user-select: none;
}
@media (min-width: 1075px) {
@@ -62,6 +71,8 @@
  display: flex;
  flex: 1 1 200px;
  margin: 8px;
+  -webkit-appearance: none;
+  -moz-appearance: none;
  appearance: none;
  background: #eee;
  padding: 10px 10px;
@@ -121,6 +132,9 @@
  justify-content: space-between;
  align-items: center;
  padding: 6px 4px;
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
  user-select: none;
  transition: background-color 0.3s ease-in-out;
  cursor: default;
@@ -168,6 +182,8 @@
  overflow-x: hidden;
}
.c-sf-block__actions__single {
+  -webkit-appearance: none;
+  -moz-appearance: none;
  appearance: none;
  border: 0 none;
  background: none;
@@ -211,6 +227,9 @@
  text-align: right;
  font-size: 12px;
  color: #585858;
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
  user-select: none;
  vertical-align: 2px;
  overflow-x: hidden;