push v0.8 to master

# Conflicts:
#	README.md

doc/customization.md

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+## Custom Score Function
+
+```js
+const index = new FlexSearchIndex({
+    resolution: 10,
+    score: function(content, term, term_index, partial, partial_index){
+        // you'll need to return a number between 0 and "resolution"
+        // score is starting from 0, which is the highest score
+        // for a resolution of 10 you can return 0 - 9
+        // ... 
+        return 3;
+    } 
+});
+```
+
+A common situation is you have some predefined labels which are related to some kind of order, e.g. the importance or priority. A priority label could be `high`, `moderate`, `low` so you can derive the scoring from those properties. Another example is when you have something already ordered and you would like to keep this order as relevance.
+
+Probably you won't need the parameters passed to the score function. But when needed here are the parameters from the score function explained:
+
+1. `content` is the whole content as an array of terms (encoded)
+2. `term` is the current term which is actually processed (encoded)
+3. `term_index` is the index of the term in the content array
+4. `partial` is the current partial of a term which is actually processed
+5. `partial_index` is the index position of the partial within the term
+
+Partials params are empty when using tokenizer `strict`. Let's take an example by using the tokenizer `full`.
+
+The content: "This is an ex[amp]()le of partial encoding"<br>
+The highlighting part marks the partial which is actually processed. Then your score function will called by passing these parameters:
+
+```js
+function score(content, term, term_index, partial, partial_index){
+    content = ["this", "is", "an", "example", "of", "partial", "encoding"]
+    term = "example"
+    term_index = 3
+    partial = "amp"
+    partial_index = 2
+} 
+```