Integrate trails color scheme into base theme

.changeset/update-theme.md

@@ -0,0 +1,6 @@
+---
+"@open-pioneer/base-theme": minor
+---
+
+Merge developments from @open-pioneer/theme.
+This package now provides the `"trails"` color scheme, among other things.

src/packages/base-theme/README.md

@@ -1,10 +1,78 @@
 # @open-pioneer/base-theme
 
-Provides the default open pioneer trails chakra theme.
+This package provides a theme that uses the "trails" color scheme.
 
-```js
-import { theme as baseTheme } from "@open-pioneer/base-theme";
+## Usage
+
+This theme is automatically used as the default theme for all open pioneer trails applications.
+
+### How to override the `trails` color scheme
+
+Import the `extendTheme` helper function:
+
+```jsx
+import { extendTheme } from "@open-pioneer/chakra-integration";
+```
+
+Define your custom `trails` (or `trails_alt`) colors:
+
+```jsx
+const colors = {
+    trails: {
+        50: "#f5edfd",
+        100: "#eedcff",
+        200: "#d6c2ea",
+        300: "#bfa8d5",
+        400: "#a890c1",
+        500: "#9177ad",
+        600: "#7b609a",
+        700: "#654986",
+        800: "#4f3373",
+        900: "#391e61"
+    }
+};
+```
+
+Use `extendTheme` function to override the `trails` colors:
+
+```jsx
+import { theme } from "@open-pioneer/base-theme";
+const customTheme = extendTheme({ colors }, theme);
+```
+
+Or use Chakra UI color schemes to override the `trails` (or `trails_alt`) colors:
+
+```jsx
+const customTheme = extendTheme(
+    {
+        colors: {
+            trails: theme.colors.gray
+        }
+    },
+    theme
+);
+```
+
+`options: gray | red | orange | yellow | green | teal | blue | cyan | purple | pink`
+
+Then pass in the custom theme in `createCustomElement`:
+
+```jsx
+createCustomElement({
+    ...,
+    theme: customTheme
+});
 ```
 
-> NOTE: This package is still under active development.
-> There will be breaking changes.
+### How to use button variants
+
+```jsx
+<Button variant="secondary">secondary</Button>
+```
+
+`options: solid | outline | ghost | link | primary | secondary | cancel`  
+`default: solid`
+
+## License
+
+Apache-2.0 (see `LICENSE` file)