refactor!: abstract part of REPL into a base implementation

lib/node_modules/@stdlib/repl/README.md

@@ -290,7 +290,6 @@ The syntax-highlighter supports the following tokens and associated theme fields
 -   **number**: numeric literals.
 -   **literal**: reserved literals (e.g., `true`, `false`, `null`, and `undefined`).
 -   **regexp**: regular expressions.
--   **command**: built-in REPL commands.
 -   **function**: function identifiers.
 -   **object**: object identifiers.
 -   **variable**: literal identifiers.

lib/node_modules/@stdlib/repl/base/README.md

@@ -0,0 +1,89 @@
+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2025 The Stdlib Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+-->
+
+# Base
+
+> Base REPL functionality.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var ns = require( '@stdlib/repl/base' );
+```
+
+#### ns
+
+Namespace containing "base" (i.e., lower-level) REPL functionality.
+
+```javascript
+var o = ns;
+// returns {...}
+```
+
+<!-- <toc pattern="*"> -->
+
+<div class="namespace-toc">
+
+</div>
+
+<!-- </toc> -->
+
+</section>
+
+<!-- /.usage -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var objectKeys = require( '@stdlib/utils/keys' );
+var ns = require( '@stdlib/repl/base' );
+
+console.log( objectKeys( ns ) );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+<!-- <toc-links> -->
+
+<!-- </toc-links> -->
+
+</section>
+
+<!-- /.links -->