Copy documentation intro to README

Author: LilithHafner

README.md

@@ -1,8 +1,66 @@
 # CodeSearch
 
-[![Stable](https://img.shields.io/badge/docs-stable-blue.svg)](https://LilithHafner.github.io/CodeSearch.jl/stable/)
+<!-- [![Stable](https://img.shields.io/badge/docs-stable-blue.svg)](https://LilithHafner.github.io/CodeSearch.jl/stable/) -->
 [![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://LilithHafner.github.io/CodeSearch.jl/dev/)
 [![Build Status](https://github.com/LilithHafner/CodeSearch.jl/actions/workflows/CI.yml/badge.svg?branch=main)](https://github.com/LilithHafner/CodeSearch.jl/actions/workflows/CI.yml?query=branch%3Amain)
 [![Coverage](https://codecov.io/gh/LilithHafner/CodeSearch.jl/branch/main/graph/badge.svg)](https://codecov.io/gh/LilithHafner/CodeSearch.jl)
 [![PkgEval](https://JuliaCI.github.io/NanosoldierReports/pkgeval_badges/C/CodeSearch.svg)](https://JuliaCI.github.io/NanosoldierReports/pkgeval_badges/C/CodeSearch.html)
 [![Aqua](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl)
+
+
+CodeSearch.jl is a package for semantically searching Julia code. Unlike plain string search
+and regex search, CodeSearch performs search operations _after_ parsing. Thus the search
+patterns `j"a + b"` and `j"a+b"` are equivalent, and both match the code `a +b`.
+
+```julia
+julia> using CodeSearch
+
+julia> j"a + b" == j"a+b"
+true
+
+julia> findfirst(j"a+b", "sqrt(a +b)/(a+ b)")
+6:9
+```
+
+The other key feature in this package is wildcard matching. You can use the character `*` to
+match any expression. For example, the pattern `j"a + *"` matches both `a + b` and
+`a + (b + c)` .
+
+```julia
+julia> Expr.(eachmatch(j"a + *", "a + (a + b), a + sqrt(2)"))
+3-element Vector{Expr}:
+ :(a + (a + b))
+ :(a + b)
+ :(a + sqrt(2))
+```
+
+Here we can see that `j"a + *"` matches multiple places, even some that nest within
+eachother!
+
+Finally, it is possible to extract the "captured values" that match the wildcards.
+
+```julia
+julia> m = match(j"a + *", "a + (a + b), a + sqrt(2)")
+CodeSearch.Match((call-i a + (call-i a + b)), captures=[(call-i a + b)])
+
+julia> m.captures
+1-element Vector{JuliaSyntax.SyntaxNode}:
+ (call-i a + b)
+
+julia> Expr(only(m.captures))
+:(a + b)
+```
+
+## How to use this package
+
+1. Create `Pattern`s with the `@j_str` macro or the
+    `CodeSearch.pattern` function.
+2. Search an `AbstractString` or a `JuliaSyntax.SyntaxNode` for whether and where that
+    pattern occurs with generic functions like `occursin`, `findfirst`, `findlast`, or
+    `findall` _OR_ extract the actual `Match`es with generic functions like `eachmatch` and
+    `match`.
+3. If you extracted an actual match, access relevant information using the public
+    `syntax_node` and `captures` fields, convert to a `SyntaxNode`, `Expr`, or
+    `AbstractString` via constructors, index into the captures directly with `getindex`, or
+    extract the indices in the original string that match the capture with
+    `indices`.