Added 5 new speakers + updated Keiji Yoshida's profile

Added 5 new speakers + updated Keiji Yoshida's profile
@bmsantosh The twitter account of the following code is incorrect (the last "i" is omitted):

```html
<a href="https://twitter.com/_yosss" target="_blank">@_yosss</a>
```

Here is a correct account:

```html
<a href="https://twitter.com/_yosssi" target="_blank">@_yosssi</a>
```