Add instructions for changing plot attributes (#49)

* Add attribute instruction plots

* Update README.md

* Delete attr_circuit_1.svg

* Update README.md

README.md

@@ -21,6 +21,36 @@ Otherwise, you might be interested to learn [how to save it as an image](https:/
 
 See more [examples](examples/circuits.jl).
 
+### Adjusting the plot attributes
+
+Various attributes of the visualizations can be altered. 
+The plot can be modifiend, if we change the following attributes
+
+- `YaoPlots.CircuitStyles.linecolor[]` for line color, default value being `"#000000"` (black color)
+- `YaoPlots.CircuitStyles.gate_bgcolor[]` for background color of square blocks, the default value being `"#FFFFFF"` (white color)
+- `YaoPlots.CircuitStyles.textcolor[]` for text color, default value being `"#000000`
+- `YaoPlots.CircuitStyles.lw[]` for line width, default value being `1pt`
+- `YaoPlots.CircuitStyles.textsize[]` for text size, default value being `16pt`
+- `YaoPlots.CircuitStyles.paramtextsize[]` for parameter text size, for parameterized gates, default value being `10pt`
+
+For example,
+
+```julia
+using YaoPlots, Yao
+YaoPlots.CircuitStyles.linecolor[] = "pink" 
+YaoPlots.CircuitStyles.gate_bgcolor[] = "yellow" 
+YaoPlots.CircuitStyles.textcolor[] = "#000080" # the navy blue color
+YaoPlots.CircuitStyles.fontfamily[] = "JuliaMono"
+YaoPlots.CircuitStyles.lw[] = 2.5pt
+YaoPlots.CircuitStyles.textsize[] = 13pt
+YaoPlots.CircuitStyles.paramtextsize[] = 8pt
+
+plot(chain(3, put(1=>X), repeat(3, H), put(2=>Y), repeat(3, Rx(π/2))))
+```
+
+![attribute_example_2](examples/attr_circuit_2.svg)
+
+
 ## Example 2: Visualize ZX-diagrams in ZXCalculus
 ```julia
 using ZXCalculus, YaoPlots