Fix toc link not working on github

[murata0705]

relate to #331

Some toc links doesn't work on github.
I couldn't find the exact cause but I think some github function changing markdown file make the problem.

If we use name attribute of a tag in markdown file, github add user-content prefix and downcase words.

example

# before
link-GET-shop-/api/shops

# after
user-content-link-get-shop-/api/shops

I tried some cases.

# work
<a href="#link-GET-shop-/api/shops">GET /api/shops</a>
<a name="user-content-link-get-shop-/api/shops">Shop Shop Search API</a>

# not work
<a href="#link-GET-shop-/api/shops/{(%23%2Fdefinitions%2Fshop%2Fdefinitions%2Fid)}">GET /api/shops/{shop_id}</a>
<a name="user-content-link-get-shop-/api/shops/{(%23%2fdefinitions%2fshop%2fdefinitions%2fid)}">Shop Shop Detail API</a>

# work
<a href="#link-GET-shop-/api/shops/{shop_id}">GET /api/shops/{shop_id}</a>
<a name="user-content-link-get-shop-/api/shops/{shop_id}">Shop Shop Search API</a>

I don't know the cause but this fix work well and I think more simple than before.