Fixed typo from PR #598 and documentation bits for set operators (#599)

* write start of L_Plus.md

* Plus and Minus docs and its notebook

* wrote doc pages for all the operators.

* fix to meet agreed format

* Created using Colaboratory

* add multiplicationDemonstration.ipynb

* add absoluteValues.ipynb

* add factorial.ipynb

* add toInt_demonstration.ipynb

* fixed absoluteValues.ipynb

* added notebook links

* fixed L_Minus.md typo

* improved these notebooks with hz66-404 suggestions

* fixed typo

* add Set_operators demonstration

* Create L_union.md

* Update Set_operators.ipynb add badge and title

* Create L_intersect.md

* fixed badge Set_operators.ipynb

* Create L_subset.md

* Update Set_operators.ipynb

Changed "subset" italics issue

* Rename addition_subtraction_examples.ipynb to addition_and_subtraction_examples.ipynb

fixed typo from recent PR

* Update Set_operators.ipynb

fix the grammar

* Create L_subsetEq.md

* Update L_subsetEq.md

* Create L_supset.md

* Create L_supsetEq.md

* Update L_supset.md

* Update Set_operators.ipynb

update the last subset to subsetEq / some grammar changed

* Update Set_operators.ipynb

* add L_in.md

* Delete docs/notebooks/Set_operators.ipynb

this file lack of "in" this keyword

* new Set_operators demonstration

* Update Set_operators.ipynb add badge and title

* Update L_in.md changed links

* Update L_intersect.md changed links

* Update L_subset.md changed links

* Update L_subsetEq.md changed links

* Update L_supset.md changed links

* Update L_supsetEq.md changed links

* Update L_union.md changed links

---------

Co-authored-by: Han Zheng <117105566+hz66-404@users.noreply.github.com>

docs/bits/operator/L_in.md

@@ -1,6 +1,10 @@
-# in (membership check)
+# in
+
+test if element is in set
 
 ```essence
-in
+find a : bool such that a = (1 in {0,1})
 ```
-The in operator is checks if the left operand is contained within the right operand. 
+This syntax is checking if 1 is in the set {0,1}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_intersect.md

@@ -0,0 +1,10 @@
+# intersect
+
+Set of elements in both sets
+
+```essence
+find A : set of int(0..6) such that A = {1,2,3} intersect {2,3}
+```
+This syntax is finding the intersection part of {1,2,3} and {2,3}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_subset.md

@@ -0,0 +1,10 @@
+# subset
+
+test if first set is strictly contained in second set (exclude two sets are equal)
+
+```essence
+find b : bool such that b = ({0,1} subset {0,1,3})
+```
+This syntax is testing if {0,1,3} contains {0,1}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_subsetEq.md

@@ -0,0 +1,10 @@
+# subsetEq
+
+test if first set is strictly contained in second set (two sets can be equal)
+
+```essence
+find b : bool such that b = ({0,1} subsetEq {0,1})
+```
+This syntax is testing if {0,1} contains {0,1}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_supset.md

@@ -0,0 +1,10 @@
+# supset
+
+test if the first set strictly contains the second set (exclude two sets are equal)
+
+```essence
+find b : bool such that b = ({2,1} supset {1})
+```
+This syntax is testing if {2,1} contains {1}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_supsetEq.md

@@ -0,0 +1,10 @@
+# supsetEq
+
+test if the first set contains the second set (two sets can be equal)
+
+```essence
+find b : bool such that b = ({2} supsetEq {2})
+```
+This syntax is testing if {2} contains {2}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).

docs/bits/operator/L_union.md

@@ -0,0 +1,10 @@
+# union
+
+Set of elements in either of the sets
+
+```essence
+find B : set of int(0..6) such that B = {1,2,3} union {3,4}
+```
+This syntax is finding the union of two sets {1,2,3} and {3,4}
+
+See it demonstrated [here](https://github.com/conjure-cp/conjure/blob/main/docs/notebooks/Set_operators.ipynb).