assets/markdown: plugins: add bitcoin documentation

markdown/How-do-I-use-it.md

@@ -172,7 +172,9 @@ See the container `times help` command for details.
 
 Plugins (pluggables) allow you to leverage `dfi` client/container APIs, libraries and environments to meet your unique needs.
 
-For more information and examples, see some of the various existing plugins (pluggables) and respective help usage, i.e.;
+Checkout this two-part client/container set of [Bitcoin plugins](#plugins-bitcoin) to see how all APIs/libraries/environments can work together in unison.
+
+For more information and other examples, see some of the various existing plugins (pluggables) and respective help usage, i.e.;
 
   - Client-side (host): `dfi <platform/user:tag> plugins help`
   - Container-side: `dfi <profile/subprofile> plugins help`
@@ -230,6 +232,90 @@ To mirror these categories, a client-side `custom` plugin directory layout is ge
     * NOTE: `root` pluggable auto-(un)loading requires a parent directory as the callable namespace (and more)
       - See docs for details: `dfi dev-tools/${USER}:default doxygen gen`
 
+#### Plugins: Bitcoin
+
+`dfi`'s bitcoin plugin is a two-part client/container set of plugins that gives you direct access to bitcoin's libbitcoinkernel (and related headers/symbols).
+
+The following demo assumes that you'll be using a fresh setup and that you've at least satisfied the required dependencies in [Installation](How-do-I-get-started.md#installation) (Docker Engine/Compose/Buildx, Bash, Git).
+
+If you're a first-time user and/or developer who simply wants a quickstart, run the following before proceeding:
+
+```bash
+git clone --depth=1 https://gitea.com/EvergreenCrypto/docker-finance docker-finance/repo
+./docker-finance/repo/client/install.bash && source ~/.bashrc
+dfi archlinux/${USER}:default gen all=all profile=testprofile/testuser confirm=no dev=on
+```
+
+##### Plugins: Bitcoin: Client
+
+Here, we prepare client-side dependencies and build everything needed for the container-side plugin:
+
+<video src="../assets/examples/webm/client-plugins-bitcoin.webm" controls></video>
+
+Shell 1:
+
+```bash
+# NOTE: editing will only be required once (unless you `gen type=build` in the future)
+dfi archlinux/${USER}:default edit type=build
+dfi archlinux/${USER}:default build type=default
+```
+
+Shell 2:
+
+```bash
+dfi archlinux/${USER}:default up
+```
+
+Shell 1:
+
+```bash
+dfi archlinux/${USER}:default plugins repo/bitcoin.bash get
+dfi archlinux/${USER}:default plugins repo/bitcoin.bash build
+```
+
+##### Plugins: Bitcoin: Container
+
+Here, we see the multiple ways the container-side plugin can be loaded and also test its functionality:
+
+<video src="../assets/examples/webm/container-root-plugins-bitcoin_cli.webm" controls></video>
+
+Shell 2 (or open a new shell into container, as seen in the demo):
+
+```bash
+dfi testprofile/testuser root
+```
+
+Within `root` interpreter:
+
+```cpp
+// NOTE:
+//   - The demo shows `btck` tab completion (which can't be put here)
+//   - semicolons are not needed, since the following is executed per line
+GetRandHash()
+dfi::plugin::load("repo/bitcoin/bitcoin.cc")
+GetRandHash()
+dfi::macro::load("repo/test/unit.C", "Random*")
+.quit
+```
+
+Shell 2:
+
+```bash
+BENCHMARK_FILTER="^Random" dfi testprofile/testuser root plugins/repo/bitcoin/bitcoin.cc 'dfi::macro::load(\"repo/test/benchmark.C\"); dfi::common::exit(0);'
+dfi testprofile/testuser root plugins/repo/bitcoin/bitcoin.cc 'dfi::macro::load(\"repo/web/server.C\")'
+```
+
+##### Plugins: Bitcoin: Web browser
+
+Here, we see a real-world visualization of what the container-side plugin can produce. In this example, with the plugin previously loaded (as seen above), we sample bitcoin's RNG:
+
+<video src="../assets/examples/webm/container-root-plugins-bitcoin_web.webm" controls></video>
+
+- Open browser to `http://127.0.0.1:8080`
+  * Default port can be changed with client-side command: `dfi archlinux/${USER}:default edit type=env`
+- Click `rng_sample` -> Enter sample amount
+- Click `reload`
+
 ### Caveats & Oddities
 
 #### Caveats & Oddities: Flow