README: add CI badge (#17)

* README: add CI badge

* github: update node version

* package: format README

* README: wording

* package: update lock

* package: npm run coverage

* github: fix coverall

* README: coverage badge

.github/workflows/coverall.yml

@@ -0,0 +1,21 @@
+on: ["push", "pull_request"]
+
+name: Test Coveralls
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Use Node.js 20.x
+        uses: actions/setup-node@v3
+        with:
+          node-version: 20.x
+      - name: Install dependencies
+        run: npm ci
+      - name: run coverage
+        run: npm run coverage
+      - name: Coveralls
+        uses: coverallsapp/github-action@v2

.github/workflows/main.yml

@@ -14,7 +14,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [19.x]
+        node-version: [20.x]
 
     steps:
       - name: "Checkout current repository"

.gitignore

@@ -3,3 +3,4 @@ dist
 *.dot
 src/*.dot
 README.html
+coverage

README.md

@@ -1,11 +1,16 @@
-# Cells: A Functional & Reactive Programming library
+# Cells: Simplified Functional & Reactive Programming
 
-`cells` is a Functional & Reactive Programming (FRP) library inspired by
-spreadsheets. This programming paradigm simplifies handling complex, dynamic
-data flows. It is particularly useful in scenarios with asynchronous data
+![CI](https://github.com/okcontract/cells/actions/workflows/main.yml/badge.svg)
+[![Coverage Status](https://coveralls.io/repos/github/okcontract/cells/badge.svg?branch=main)](https://coveralls.io/github/okcontract/cells?branch=main)
+
+Functional & Reactive programming (FRP) simplifies handling complex, dynamic
+data flows: It is particularly useful in scenarios with asynchronous data
 sources, such as user interfaces or real-time data feeds.
 
-![cells are either values or functions](./assets/cells.svg)
+`cells` is a simplified Functional & Reactive (but not strictly FRP) library
+inspired by spreadsheets.
+
+![cells are either *values* or *functions*](./assets/cells.svg)
 
 `cells` focuses on automation as it transparently manages:
 
@@ -15,8 +20,8 @@ sources, such as user interfaces or real-time data feeds.
 - pointers
 
 Although it is a fully independent library, `cells` can be a powerful drop-in
-replacement for Svelte stores. The build artifacts are currently at 19.5 kB
-(6 kB gzipped).
+replacement for Svelte stores. The build artifacts are currently at 19.5 kB (6
+kB gzipped).
 
 ## Walkthrough
 
@@ -61,12 +66,13 @@ Note that:
   values are defined. If you need to immediately return a value, use `null`
   instead.
 - At any time, the actual cell value is accessible through `cell.value`
-  (possibly undefined) but it's advisable to avoid relying on a value that could
-  be updated at any moment.
+  (possibly undefined) but it's advisable to avoid relying on a value that
+  could be updated at any moment.
 
 ## Subscriptions
 
-You can define subscribers functions to be called whenever a cell value change.
+You can define subscribers functions to be called whenever a cell value
+change.
 
 ```ts
 const cellA = sheet.new(1);
@@ -81,9 +87,9 @@ unsubscribe();
 ```
 
 When using `cells` in Svelte files, you can use the `$cell` sugar to subscribe
-to a cell value for display. Note that there is a initial `undefined` value when
-using that sugar as the reactive subscription are initially output by the Svelte
-compiler as `let $cell;`.
+to a cell value for display. Note that there is a initial `undefined` value
+when using that sugar as the reactive subscription are initially output by the
+Svelte compiler as `let $cell;`.
 
 Unlike Svelte, subscriptions are called in transactional batches, i.e. `cells`
 wait until all updates are propagated in the `Sheet` to dispatch notifications
@@ -154,10 +160,11 @@ const counter = proxy.new(0);
 counter.update((prev) => prev + 1);
 ```
 
-Note that `update` functions should return new arrays and objects, for instance
-using spread operators `[...prev, new]` and `{...prev, field: new}`.
+Note that `update` functions should return new arrays and objects, for
+instance using spread operators `[...prev, new]` and `{...prev, field: new}`.
 
-If you need more complex imperative updates, we suggest you to use `immer`:
+If you need more complex imperative updates, we suggest you to use
+[immer](https://github.com/immerjs/immer):
 
 ```typescript
 import { produce } from "immer";
@@ -170,24 +177,30 @@ cell.update((prev) => produce(prev, patch));
 
 # Design & Philosophy
 
-The design and philosophy of cells are influenced by frameworks like `RxJS`,
-`MobX`, and `Recoil`, with increased automation. Our focus is to streamline the
-developer experience, reduce the boilerplate and complexity often encountered in
-state management and reactive programming.
+The design and philosophy of `cells` comes from frameworks such as `RxJS`,
+`MobX`, and `Recoil`. Our main objective is to enhance developer experience by
+simplifying the complexity typically associated with state management and
+reactive programming.
+
+We aim for ease of use and correction, so chasing down any bug is our top
+priority.
+
+A non-goal is high-performance (we're not a tensor library!): `cells` is
+slower than any direct implementation and should not be used for
+computationally intensive tasks. However, `cells` optimizes the global
+computation within a program, potentially leading to more optimal execution
+than can be achieved through imperative computations from manually organized
+functions or modules.
 
 # About
 
 `cells` is built at [OKcontract](https://okcontract.com) and is released under
 the MIT license.
 
-We aim for ease of use and correction. Chasing down any bug is our top priority.
-
-A non-goal for now is high-performance: `cells` is slower than any direct
-implementation and should not be used for computationally intensive tasks.
-
 Contributors are welcome, feel free to submit PRs directly for small changes.
-You can also reach out in our [Discord](https://discord.gg/Cun5aF7k) or contact
-us on [Twitter](https://x.com/okcontract) in advance for larger contributions.
+You can also reach out in our [Discord](https://discord.gg/Cun5aF7k) or
+contact us on [Twitter](https://x.com/okcontract) in advance for larger
+contributions.
 
 This work is supported in part by a RFG grant from
 [Optimism](https://optimism.io).