Update README.md

Initial descriptions

README.md

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-# perline
-Wrap text at logical places. Sentence or sub-unit per line.
+# Perline
+The project combines the Perline text style,
+  a two-way converter, and a live playground site.
+For soft wrap documents, Perline simply means
+  "one sentence per line".
+For documents with maximum line widths,
+  any long sentences split at logical places over further lines.
+In Perline, all lines hold a self-contained part of a sentence.
+The two-way converter wraps normal text to Perline,
+  and unwraps Perline to normal text.
+The live playground edits and presents text in both formats.
+
+Visit [the Perline Website](https://perline.pages.dev/).