Add oembed tags. Fix sharing and copy link button. Add text and file viewer

svelte/src/filesystem/viewers/Text.svelte

@@ -0,0 +1,53 @@
+<script>
+import { fs_file_url } from "../FilesystemUtil";
+
+export let state
+let text_pre
+
+$: set_file(state.base)
+
+export const set_file = file => {
+	console.debug("Loading text file", file.name)
+
+	if (file.size > 1 << 22) { // File larger than 4 MiB
+		text_pre.innerText = "File is too large to view online.\nPlease download and view it locally."
+		return
+	}
+
+	fetch(fs_file_url(state.root.id, file.path)).then(resp => {
+		if (!resp.ok) { return Promise.reject(resp.status) }
+		return resp.text()
+	}).then(resp => {
+		text_pre.innerText = resp
+	}).catch(err => {
+		text_pre.innerText = "Error loading file: " + err
+	})
+}
+</script>
+
+
+<div class="container">
+	<pre bind:this={text_pre}>
+		Loading...
+	</pre>
+</div>
+
+<style>
+.container {
+	background: var(--body_color);
+	text-align: left;
+	height: 100%;
+	width: 100%;
+	line-height: 1.5em;
+	overflow-y: auto;
+	overflow-x: hidden;
+}
+.container > pre {
+	margin: 0;
+	padding: 10px;
+	white-space: pre-wrap;
+	overflow: hidden;
+	border: none;
+	font-size: 0.9em;
+}
+</style>