add links to various browser-oriented libs from mcaptcha

content/docs/API/browser.md

@@ -1,5 +1,5 @@
 ---
-title: "Browser library"
+title: "Browser libraries"
 description: "API documenttion for mCaptcha WASM library"
 lead: ""
 date: 2021-03-11
@@ -13,10 +13,42 @@ weight: 110
 toc: true
 ---
 
+The browser part of mCaptcha is divided into three components.
+
+- Glue code
+- Widget program
+- Proof-of-Work libraries(WebAssembly and JavaScript polyfill)
+
+## Glue code
+
+This is the code that links mCaptcha with your website's frontend code.
+It creates an `iframe` containing the mCaptcha widget and injects the
+received verification proof token into a hidden input field.
+
+Support is available for various frameworks, see
+[`mCaptcha/glue`](https://github.com/mCaptcha/glue) for the full list.
+
+For frameworks without official support, a low-level library,
+[`@mcaptcha/core-glue`](https://www.npmjs.com/package/@mcaptcha/core-glue),
+can be used to implement support.
+
+## Widget Program
+
+This part is served by the mCaptcha backend. It fetches PoW config from
+the backend, generates proof and submits it for verification. If
+verification is successful, it sends a message containing the
+verification proof token to the parent window, assuming it's loaded as
+an `iframe`.
+
+- Source code:
+  [`mCaptcha/mCaptcha/templates/widget`](https://github.com/mCaptcha/mCaptcha/tree/master/templates/widget)
+
 WebAssembly library which generates Proofs of Work for mCaptcha systems.
 
+## Proof-of-Work(PoW) library
 
-## Versions
+WebAssembly bindings([`mCaptcha/pow_wasm`](https://github.com/mCaptcha/pow_wasm)) are available for the main rust library([`mCaptcha/pow_sha256`](https://github.com/mCaptcha/pow_sha256)).
 
-- [master-branch](https://mcaptcha.github.io/browser/mCaptcha_browser/index.html)
-- [0.1.0](/api-docs/browser/0.1.0/mCaptcha_browser/index.html)
+For browsers without support WebAssembly, a
+polyfill([`pow_sha256-polyfill`](https://github.com/mCaptcha/pow_sha256-polyfill))
+is available.