hgweb: use strict equals, remove non-breaking space in followlines.js

The first hunk had a non-breaking space character just before "{", it's not an
error or anything, but let's fix it while we're at it. (This corresponds to
"nonbsp" option of jshint).

Hunks 2 and 3 change "==" (equals operator) to "===" (strict equals operator).
The difference between them is that the latter doesn't do any type coercions.
It's handy to compare string '1' to number 1 sometimes, but most of the time
using "==" is inadvertent and can be replaced by an explicit type conversion.
(This corresponds to "eqeqeq" option of jshint).

Most of this file already uses strict equals operator, and in the code affected
type coercion is not needed, because tagName and selectableTag are both strings
and endId and startId are both numbers.

mercurial/templates/static/followlines.js

@@ -13,7 +13,7 b" document.addEventListener('DOMContentLoa"
     }
     // URL to complement with "linerange" query parameter
     var targetUri = sourcelines.dataset.logurl;
-    if (typeof targetUri === 'undefined') {
+    if (typeof targetUri === 'undefined') {
         return;
     }
 
@@ -114,7 +114,7 b" document.addEventListener('DOMContentLoa"
         if (parent === null) {
             return null;
         }
-        if (element.tagName == selectableTag && parent.isSameNode(sourcelines)) {
+        if (element.tagName === selectableTag && parent.isSameNode(sourcelines)) {
             return element;
         }
         return selectableParent(parent);
@@ -182,7 +182,7 b" document.addEventListener('DOMContentLoa"
 
             // compute line range (startId, endId)
             var endId = parseInt(endElement.id.slice(1));
-            if (endId == startId) {
+            if (endId === startId) {
                 // clicked twice the same line, cancel and reset initial state
                 // (CSS, event listener for selection start)
                 removeSelectedCSSClass();