add codecov badge

Author: tomchen

README.md

@@ -1,6 +1,6 @@
 # BDF Parser
 
-[![PyPI package](https://img.shields.io/badge/pip%20install-bdfparser-brightgreen)](https://pypi.org/project/bdfparser/) [![Actions Status](https://github.com/tomchen/bdfparser/workflows/Test/badge.svg)](https://github.com/tomchen/bdfparser/actions) [![License](https://img.shields.io/github/license/tomchen/bdfparser)](https://github.com/tomchen/bdfparser/blob/master/LICENSE)
+[![PyPI package](https://img.shields.io/badge/pip%20install-bdfparser-brightgreen)](https://pypi.org/project/bdfparser/) [![Actions Status](https://github.com/tomchen/bdfparser/workflows/Test/badge.svg)](https://github.com/tomchen/bdfparser/actions) [![codecov](https://codecov.io/gh/tomchen/bdfparser/branch/master/graph/badge.svg?token=IMVVQEC04H)](https://codecov.io/gh/tomchen/bdfparser) [![License](https://img.shields.io/github/license/tomchen/bdfparser)](https://github.com/tomchen/bdfparser/blob/master/LICENSE)
 
 BDF (Glyph Bitmap Distribution; [Wikipedia](https://en.wikipedia.org/wiki/Glyph_Bitmap_Distribution_Format); [Spec](https://font.tomchen.org/bdf_spec/)) format bitmap font file parser library in Python. It has [`Font`](https://font.tomchen.org/bdfparser_py/font), [`Glyph`](https://font.tomchen.org/bdfparser_py/glyph) and [`Bitmap`](https://font.tomchen.org/bdfparser_py/bitmap) classes providing more than 30 enriched API methods of parsing BDF fonts, getting their meta information, rendering text in any writing direction, adding special effects and manipulating bitmap images. It works seamlessly with [PIL / Pillow](https://pillow.readthedocs.io/en/stable/) and [NumPy](https://numpy.org/).
 
@@ -52,4 +52,4 @@ im_ac = Image.frombytes('1',
 im_ac.save("font_preview.png", "PNG")
 ```
 
-You probably understand what I did in these examples. If you don't, go to [bdfparser's documentation website](https://font.tomchen.org/bdfparser_py/).
+You probably understand what I did in these examples. Whether you do or not, go to [bdfparser's documentation website](https://font.tomchen.org/bdfparser_py/).