feat: deephaven.ui plugin prototype initial checkin (#47)

- deephaven.ui plugin prototype initial checkin has some extremely basic
cases implemented (Fixes #51)
- Needs my ui-plugin-prototype branch to work correctly (as that how the
JS side is loading components):
https://github.com/mofojed/web-client-ui/tree/ui-plugin-prototype
- The examples in the `plugins/ui/examples` folder should work
- Included DESIGN.md which is the discussion/notes from the google doc
discussion
- Added some TODO notes about things that require follow up
- Install as you would other plugins

Implemented so far:
- Basic `@ui.component` decorator (Fixes #54)
- Creates a `FunctionElement` object when called. `FunctionElement` is
then "rendered" (e.g. function is run) when the `FunctionElement` object
is exported (see `FunctionElementMessageStream`) (Fixes #52)
  - Exports a document tree (Fixes #53)
- Basic hooks are implemented (Fixes #55), along with tests. See the
`hooks` folder for the hooks available (`use_state`, `use_memo`,
`use_effect`, etc)
- `text_field` and `text` types are implemented
- Basic HTML elements (Fixes #56)
- Create JS Plugin side (Fixes #57)
- DashboardPlugin to open components created by @ui.component (Fixes
#58)
- HTML JS component handles any raw HTML component (Fixes #60)

.gitignore

@@ -1,3 +1,12 @@
 node_modules
 .vscode/
 tsconfig.tsbuildinfo
+
+# Ignore user IntelliJ settings
+.idea/
+
+# Ignore users local python venvs
+.venv/
+
+# Ignore any local tox virtualenvs
+.tox/

README.md

@@ -138,4 +138,4 @@ Using the path to your local deephaven-js-plugins repo where the manifest.json i
 START_OPTS="-Ddeephaven.jsPlugins.resourceBase=<deephaven-plugins-path>deephaven-js-plugins/plugins" ./gradlew server-jetty-app:run
 ```
 
-The deephaven IDE can then be opened at http://localhost:10000/ide/, with your plugins ready to use.
+The Deephaven IDE can then be opened at http://localhost:10000/ide/, with your plugins ready to use.