policies.json: install uBlock origin by default (MR 19)

Here's something controversial. Install the wide-spectrum blocker uBlock
origin by default. This enables blocking of ads, trackers and malware
sites. I think these should be blocked for several reasons:

1. Performance on mobile devices

It's clear when browsing the web with this add-on, that there is a major
performance benefit in blocking advertising and tracking on websites. We
don't have these resources to waste on Mobile Linux.

2. Privacy

From uBlock origin's README.md:
> [...] it's important to note that using a blocker is NOT theft. Don't fall
> for this creepy idea. The ultimate logical consequence of blocking = theft
> is the criminalisation of the inalienable right to privacy.

> Ads, "unintrusive" or not, are just the visible portions of privacy-invading
> apparatus entering your browser when you visit most sites nowadays. uBlock
> Origin's main goal is to help users neutralize such privacy-invading
> apparatus — in a way that welcomes those users who don't wish to use more
> technical, involved means (such as uMatrix).

3. Manipulation

Modern advertising platforms are used to manipulate people in the scale
of influencing elections of world leaders. From Cambridge Analytica and
similar companies' perspective, one of the workflows is showing the user
an advertisement, then monitoring search queries to determine if the ad
was effective, then adjusting the ad to convince you better to vote for
a certain party, repeat. This has severe negative effects on society,
for people unfamiliar with the topic I recommend watching the movies
"The Great Hack" and "The Social Dilemma". The mentioned workflow is
described in the "Your Undivided Attention" podcast, episode 10, "Rock
the Voter" in an interview with a former Cambridge Analyticer insider.

Related: https://github.com/gorhill/uBlock
Related: cab6a5076c/README.md (policiesjson-45)
Related: https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

src/policies.json

@@ -123,6 +123,13 @@
             "ExtensionRecommendations": false,
             "FeatureRecommendations": false,
             "UrlbarInterventions": false
+        },
+
+        "ExtensionSettings": {
+            "uBlock0@raymondhill.net": {
+                "installation_mode": "normal_installed",
+                "install_url": "https://addons.mozilla.org/firefox/downloads/latest/ublock-origin/latest.xpi"
+            }
         }
     }
 }