Selection to clipboard (#124)

* selection-to-text example

* update icon

* update icon

* use clipboard icon

* update with requested changes

* updated strict version and wrapped clipboard copy in setTimeout to force permissions

* add note about clipboardWrite permissions inside browser event. removed permissions and setTimeout

selection-to-clipboard/README.md

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+# selection-to-clipboard
+
+## What it does
+
+This extension includes:
+
+* a content script, "content-script.js", that is injected into all pages
+
+The content script listens for text selections in the page it's attached to and copies the text to the clipboard on mouse-up.
+
+## What it shows
+
+* how to inject content scripts declaratively using manifest.json
+* how to write to the [clipboard](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Interact_with_the_clipboard)
+
+## Note
+* If the `copySelection` function was in a browser event `clipboardWrite` permissions would be required e.g.
+```
+"permissions": ["clipboardWrite"]
+```
+See [Interact with the clipboard](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Interact_with_the_clipboard.)

selection-to-clipboard/content-script.js

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+/*
+copy the selected text to clipboard
+*/
+function copySelection(e) {
+    var selectedText = window.getSelection().toString().trim();
+
+    if (selectedText) {
+        document.execCommand("Copy");
+    }
+}
+
+/*
+Add copySelection() as a listener to mouseup events.
+*/
+document.addEventListener("mouseup", copySelection);

selection-to-clipboard/icons/LICENSE

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+
+The "page-32.png" and "page-48.png" icons are taken from the miu iconset created by Linh Pham Thi Dieu, and are used under the terms of its license: http://linhpham.me/miu/.

selection-to-clipboard/manifest.json

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+{
+    "manifest_version": 2,
+    "name": "selection-to-clipboard",
+    "description": "Example of WebExtensionAPI for writing to the clipboard",
+    "version": "1.0",
+    "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/selection-to-clipboard",
+
+    "icons": {
+        "48": "icons/clipboard-48.png"
+    },
+
+    "applications": {
+        "gecko": {
+            "strict_min_version": "51.0a1"
+        }
+    },
+
+    "content_scripts": [{
+        "matches": ["<all_urls>"],
+        "js": ["content-script.js"]
+    }]
+}