[TASK] Unify placeholder syntax (#268)

Use `<placeholder>` as default placeholder style in
URLs since it's standard in Backus–Naur form.

To avoid URL linking, apply the reST directive `:samp:`.

.editorconfig

@@ -1,5 +1,5 @@
 
-# EditorConfig is awesome: http://EditorConfig.org
+# EditorConfig is awesome: https://EditorConfig.org
 #
 # Use as master: https://github.com/TYPO3-Documentation/T3DocTeam/blob/master/.editorconfig
 

Documentation/.editorconfig

@@ -1,4 +1,4 @@
-# EditorConfig is awesome: http://EditorConfig.org
+# EditorConfig is awesome: https://EditorConfig.org
 
 # top-most EditorConfig file? false = no!
 root = false

Documentation/Legacy/Index.rst

@@ -40,7 +40,7 @@ automatically install the new source code.
 Major Upgrades - Symlink The Core
 =================================
 
-Go to `http://typo3.org/download/ <http://typo3.org/download/>`_ and download
+Go to https://typo3.org/download/ and download
 the source package of the new TYPO3 version.
 
 Extract the package on your web server and, in your TYPO3 document root,

Documentation/MigrateToComposer/MigrationSteps.rst

@@ -218,7 +218,7 @@ Install extension from TER
 
 If the extension is not available on packagist, the good news is: All
 TER extensions are available via Composer! That's, why we added
-`https://composer.typo3.org/` as repository to our :file:`composer.json`
+:samp:`https://composer.typo3.org/` as repository to our :file:`composer.json`
 some lines above. There are little naming conventions:
 
 *  Vendor name is `typo3-ter`.
@@ -239,7 +239,7 @@ https://composer.typo3.org/satis.html.
 .. note ::
 
     If you do not include any packages this way, you can remove the
-    repository block named `https://composer.typo3.org` from your
+    repository block named :samp:`https://composer.typo3.org` from your
     :file:`composer.json` to improve speed.
 
 Install extension from version control system (e.g. GitHub, Gitlab, ...)