Improvement to docs (#698)

* Docs : Clarify `addslashes` filter
* Docs : Clarify `slugify` filter

docs/content/docs/_index.md

@@ -789,21 +789,20 @@ the `from` string replaced with the `to` string.
 Example: `{{ name | replace(from="Robert", to="Bob")}}`
 
 #### addslashes
-Adds slashes before quotes.
+Adds slashes before single quote (`'`), double quote (`"`) and slash (`\`) chars.
 
 Example: `{{ value | addslashes }}`
 
-If value is "I'm using Tera", the output will be "I\\'m using Tera".
+If value is \`Alice said, "I'm using \ in Tera"\`, the output will be \`Alice said, \\"I\\'m using \\\\ in Tera\\"\`.
 
 #### slugify
 Only available if the `builtins` feature is enabled.
 
-Transforms a string into ASCII, lowercases it, trims it, converts spaces to hyphens and
-removes all characters that are not numbers, lowercase letters or hyphens.
+Transforms a string into ASCII, lowercases it, trims it, converts all characters that are not numbers or lowercase letters to hyphens, replaces continuous sequence of hyphens with a single hyphen and removes leading and trailing hyphens if any.
 
 Example: `{{ value | slugify }}`
 
-If value is "-Hello world! ", the output will be "hello-world".
+If value is "  -This-- Is तेरा!   ", the output will be "this-is-teraa".
 
 #### title
 Capitalizes each word inside a sentence.