(core) Showing links in text cells

Summary:
When there is a link in a text cell (and formula cells), it will be
rendered with a little clickable icon wrapped in the anchor tag
with a proper link. Only links that starts with https? will be
rendered as links.

Links are shown in a Text and Formula fields, inside a GridView,
CardView and in the Import preview dialog.

Test Plan: Browser tests

Reviewers: alexmojaki

Reviewed By: alexmojaki

Subscribers: dsagal, alexmojaki

Differential Revision: https://phab.getgrist.com/D3070

app/client/lib/textUtils.ts

@@ -0,0 +1,47 @@
+// There are many regex for matching URL, but non seem to be the correct solution.
+// Here we will use very fast and simple one.
+// Tested most of the regex solutions mentioned in this post
+// https://stackoverflow.com/questions/37684/how-to-replace-plain-urls-with-links.
+// The best one was http://alexcorvi.github.io/anchorme.js/, which still wasn't perfect.
+// The best non regex solution was https://github.com/Hypercontext/linkifyjs, but it feels a little too heavy.
+// Some examples why this is better or worse from other solution:
+/**
+
+For 'http://www.uk,http://www.uk'
+'OurRegex' [ 'http://www.uk', 'http://www.uk' ]
+'Anchrome' [ 'http://www.uk,http://www.uk' ]
+'linkify' [ 'http://www.uk,http://www.uk' ]
+'url-regex' [ 'http://www.uk', 'http://www.uk' ]
+
+For 'might.it be a link'
+'OurRegex' []
+'Anchrome' [ 'might.it' ]
+'linkify' [ 'http://might.it' ]
+'url-regex' []
+
+For 'Is this correct.No it is not'
+'OurRegex' []
+'Anchrome' [ 'correct.No' ]
+'linkify' [ 'http://correct.No' ]
+'url-regex' []
+
+For 'Link (in http://www.uk?)'
+'OurRegex' [ 'http://www.uk' ]
+'Anchrome' [ 'http://www.uk' ]
+'linkify' [ 'http://www.uk' ]
+'url-regex' [ 'http://www.uk?)' ]
+*/
+
+// Match http or https then domain name (with optional port) then any text that ends with letter or number.
+export const urlRegex = /(https?:\/\/[A-Za-z\d][A-Za-z\d-.]*(?!\.)(?::\d+)?(?:\/[^\s]*)?[\w\d/])/;
+
+/**
+ * Detects URLs in a text and returns list of tokens { value, isLink }
+ */
+export function findLinks(text: string): Array<{value: string, isLink: boolean}> {
+  if (!text) {
+    return [{ value: text, isLink: false }];
+  }
+  // urls will be at odd-number indices
+  return text.split(urlRegex).map((value, i) => ({ value, isLink : (i % 2) === 1}));
+}