fix various links in documentation

These probably work in Gitbook to some extent but they don't work on
GitHub. In most places of the documentation files are referenced
via their source files (`.md`) and I assume Gitbook deals fine with that

For cljdoc the correct links are required to properly fix links that are
broken when rendering the document on different URLs.

doc/coercion/coercion.md

@@ -39,7 +39,7 @@ Reitit ships with the following coercion modules:
 * `reitit.coercion.schema/coercion` for [plumatic schema](https://github.com/plumatic/schema)
 * `reitit.coercion.spec/coercion` for both [clojure.spec](https://clojure.org/about/spec) and [data-specs](https://github.com/metosin/spec-tools#data-specs)
 
-Coercion can be attached to route data under `:coercion` key. There can be multiple `Coercion` implementations within a single router, normal [scoping rules](../basics/route_data.html#nested-route-data) apply.
+Coercion can be attached to route data under `:coercion` key. There can be multiple `Coercion` implementations within a single router, normal [scoping rules](../basics/route_data.md#nested-route-data) apply.
 
 ## Defining parameters
 

doc/ring/coercion.md

@@ -18,7 +18,7 @@ Reitit ships with the following coercion modules:
 * `reitit.coercion.schema/coercion` for [plumatic schema](https://github.com/plumatic/schema)
 * `reitit.coercion.spec/coercion` for both [clojure.spec](https://clojure.org/about/spec) and [data-specs](https://github.com/metosin/spec-tools#data-specs)
 
-Coercion can be attached to route data under `:coercion` key. There can be multiple `Coercion` implementations within a single router, normal [scoping rules](../basics/route_data.html#nested-route-data) apply.
+Coercion can be attached to route data under `:coercion` key. There can be multiple `Coercion` implementations within a single router, normal [scoping rules](../basics/route_data.md#nested-route-data) apply.
 
 ## Defining parameters and responses
 
@@ -137,7 +137,7 @@ Invalid response:
 
 ### Optimizations
 
-The coercion middleware are [compiled againts a route](compiling_middleware,md). In the middleware compilation step the actual coercer implementations are constructed for the defined models. Also, the middleware doesn't mount itself if a route doesn't have `:coercion` and `:parameters` or `:responses` defined.
+The coercion middleware are [compiled againts a route](compiling_middleware.md). In the middleware compilation step the actual coercer implementations are constructed for the defined models. Also, the middleware doesn't mount itself if a route doesn't have `:coercion` and `:parameters` or `:responses` defined.
 
 We can query the compiled middleware chain for the routes:
 

doc/ring/swagger.md

@@ -31,7 +31,7 @@ Coercion keys also contribute to the docs:
 | :parameters   | optional input parameters for a route, in a format defined by the coercion
 | :responses    | optional descriptions of responess, in a format defined by coercion
 
-There is a `reitit.swagger.swagger-feature`, which acts as both a `Middleware` and an `Interceptor` that is not participating in any request processing - it just defines the route data specs for the routes it's mounted to. It is only needed if the [route data validation](route_data_validation.html) is turned on.
+There is a `reitit.swagger.swagger-feature`, which acts as both a `Middleware` and an `Interceptor` that is not participating in any request processing - it just defines the route data specs for the routes it's mounted to. It is only needed if the [route data validation](route_data_validation.md) is turned on.
 
 ## Swagger spec
 
@@ -197,7 +197,7 @@ http://localhost:3000 should render now the swagger-ui:
 
 ## Advanced
 
-Route data in path `[:swagger :id]` can be either a keyword or a sequence of keywords. This enables one route to be part of multiple swagger apis. Normal route data [scoping rules](../basics/route_data.html#nested-route-data) rules apply.
+Route data in path `[:swagger :id]` can be either a keyword or a sequence of keywords. This enables one route to be part of multiple swagger apis. Normal route data [scoping rules](../basics/route_data.md#nested-route-data) rules apply.
 
 Example with: